fixrule(text_block_heading): Reduce false positives on block headings

[shunguoy]

The following formats should be use for the release notes and PRs.

Rule/Engine updates:
fixrule(text_block_heading) Reduce false positives on block headings

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• Rule bug: text_block_heading

This PR is related to the following issue(s):

• fixes Revisit: text_block_heading - can we tighten scope? #1638

Additional information can be found here:

Testing reference:

filter to the Requirement "1.3.1 Info and Relationships" and "Needs Review"
Test case 1: test/v2/checker/accessibility/rules/text_block_heading_ruleunit/text_style.html
After the fix, 5 new NR messages appear: like "Confirm this text 'Fake Heading 1' is used as a heading and if so, modify to use a heading element or role"
Test case 2: test/v2/checker/accessibility/rules/text_block_heading_ruleunit/text_ignore.html
After the fix, the NR message disappear: "Check if this text should be marked up as a heading: test options test 0 test 1 test 2"

I have conducted the following for this PR:

• I validated this code in Chrome and FF
• I validated this fix in my local env
• I provided details for testing
• This PR has been reviewed and is ready for test
• I understand that the title of this PR will be used for the next release notes.