[google_maps_flutter] Modified README.md to fix minor syntax issues

[DEVSOG12]

I fixed minor code style issue in the example. e.g. change final to const because final wasn't neccessary in the case.

• Fixed minor code style issues in the README.md

Pre-launch Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the Tree Hygiene wiki page, which explains my responsibilities.
• I read and followed the relevant style guides and ran the auto-formatter. (Unlike the flutter/flutter repo, the flutter/plugins repo does use dart format.)
• I signed the CLA.
• The title of the PR starts with the name of the plugin surrounded by square brackets, e.g. [shared_preferences]
• I listed at least one issue that this PR fixes in the description above.
• I updated pubspec.yaml with an appropriate new version according to the pub versioning philosophy, or this PR is exempt from version changes.
• I updated CHANGELOG.md to add a description of the change, following repository CHANGELOG style.
• I updated/added relevant documentation (doc comments with ///).
• [] I added new tests to check the change I am making, or this PR is test-exempt.
• [] All existing and new tests are passing.

If you need help, consider asking for advice on the #hackers-new channel on Discord.

[stuartmorgan]

Thanks for the contribution!

Any changes to code in READMEs needs to use code excerpts, so this will need to be converted as described in that documentation as part of changing it.

[DEVSOG12]

Thank you @stuartmorgan!

I have added the code excerpts to the README.

[stuartmorgan]

The excerpt process is failing in CI; it looks like you didn't set a path-base. Did this actually work when you ran it locally?

I'm going to mark this as a draft, since it's not passing CI; please feel free to mark it for review again once it's passing. Note that as part of fixing CI you'll need to do several steps that you checked off in the checklist but didn't actually do:

• I updated pubspec.yaml with an appropriate new version according to the pub versioning philosophy, or this PR is exempt from version changes.
• I updated CHANGELOG.md to add a description of the change, following repository CHANGELOG style.

Please also do this as well:

• The title of the PR starts with the name of the plugin surrounded by square brackets, e.g. [shared_preferences]

(In the future, please follow the checklist, rather than just checking items in it; it's part of the template for a reason.)

[DEVSOG12]

@stuartmorgan I have fixed all the issues.

[flutter-dashboard]

It looks like this pull request may not have tests. Please make sure to add tests before merging. If you need an exemption to this rule, contact Hixie on the #hackers channel in Chat (don't just cc him here, he won't see it! He's on Discord!).

If you are not sure if you need tests, consider this rule of thumb: the purpose of a test is to make sure someone doesn't accidentally revert the fix. Ask yourself, is there anything in your PR that you feel it is important we not accidentally revert back to how it was before your fix?

Reviewers: Read the Tree Hygiene page and make sure this patch meets those guidelines before LGTMing.

[stuartmorgan]

Sorry, I missed the earlier update. Could you address the remaining CI issues (here and here)?

[stuartmorgan]

Please also remove this package from script/configs/temp_exclude_excerpt.yaml now that it's been converted over.

Otherwise, this looks great, thanks for contributing this!

[DEVSOG12]

@stuartmorgan I have made the change, but only one test fails.

[stuartmorgan]

I re-added the existing CHANGELOG entries that you deleted; with that, this LGTM. Thanks!

(No tests are failing, that's just the tree status.)

[stuartmorgan]

@tarrinneal or @ditman could you do the secondary review on this README conversion to excerpts?

[tarrinneal]

Looks solid to me, it's cool to see the excerpts rules catching issues with the readme code ( with the help of @DEVSOG12 of course).