docs: updated statement on spring test support

[megglos]

Description

Updates statement on test support, reflecting the 8.6.7 test support module availability.

Related issues

closes camunda/camunda#26599

Definition of Done

Not all items need to be done depending on the issue and the pull request.

Code changes:

• The changes are backwards compatibility with previous versions
• If it fixes a bug then PRs are created to backport the fix

Testing:

• There are unit/integration tests that verify all acceptance criterias of the issue
• New tests are written to ensure backwards compatibility with further versions
• The behavior is tested manually

Documentation:

• Javadoc has been written
• The documentation is updated

[github-actions]

Test Results

 41 files  ±0   41 suites  ±0   23s ⏱️ -1s
134 tests ±0  102 ✅ ±0  0 💤 ±0  0 ❌ ±0  32 🔥 ±0 
426 runs  ±0  330 ✅ ±0  0 💤 ±0  0 ❌ ±0  96 🔥 ±0 

For more details on these errors, see this check.

Results for commit b0b325d. ± Comparison against base commit 49f9802.

♻️ This comment has been updated with latest results.

[saig0]

⚠️ Let's wait with the merging until the docs PR is published. Otherwise, the link to the docs has an invalid target.

[megglos]

docs PR is merged and being published, let's merge this as well.

[megglos]

CI is failing but this change is not CI related, will still merge and handle CI separately.

gencode 4.29.3, runtime 4.29.2. Runtime version cannot be older than the linked gencode version. [in thread "main"]

[megglos]

follow-up on ci failure #1421