fix(label): label now only takes up as much space as needed when slotted

[liamdebeasi]

Pull request checklist

Please check if your PR fulfills the following requirements:

• Tests for the changes have been added (for bug fixes / features)
• Docs have been reviewed and added / updated if needed (for bug fixes / features)
• Build (npm run build) was run locally and any changes were pushed
• Lint (npm run lint) has passed locally and any fixes were made for failures

Pull request type

Please check the type of change your PR introduces:

• Bugfix
• Feature
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Documentation content changes
• Other (please describe):

What is the current behavior?

ion-label components slotted in ion-item always had flex: 1. This was fine for labels at the start, but labels slotted in the end slot ended up taking up ~50% of the item width which did not look correct.

Issue Number: resolves #23806

main	branch

What is the new behavior?

• Labels in the end slot no longer get flex: 1

Does this introduce a breaking change?

• Yes
• No

Other information