Remove graduated and removed features from api incubator README

[thswlsqls]

Fixes #8920

Description

• Remove "Event API" from the api/incubator/README.md intro. Drop event API / SDK #7053 removed the Event API and its README section but left the intro text.
• Remove the "Check if logger/tracer is enabled" bullets. Stabilize enabled api #8200 moved isEnabled to the stable Logger and Tracer APIs.
• Remove "Check if instrument is enabled before recording measurements" from the ContextPropagator section. Add APIs to determine if tracer, logger, instruments are enabled #6502 added it to the wrong section, and Stabilize enabled api #8200 also moved it to the stable API.
• Fix the "boilerplace" typo.
• Update the incubator row in the root README.md API table to drop "Event API".
• Follows earlier graduation cleanups (Stabilize log any value #6591, Fix incubator docs #6505).

Testing done

• Docs-only, test-exempt: no test added.
• ./gradlew :spotlessMiscCheck :api:incubator:spotlessMiscCheck passed.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.64%. Comparing base (e806a81) to head (59d8108).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##               main    #8922   +/-   ##
=========================================
  Coverage     90.64%   90.64%           
  Complexity    10876    10876           
=========================================
  Files          1015     1015           
  Lines         29712    29712           
  Branches       3874     3874           
=========================================
+ Hits          26931    26933    +2     
+ Misses         1864     1863    -1     
+ Partials        917      916    -1     

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Pull request dashboard status

Merged · refreshed 2026-10-09 17:43 UTC

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