update SemConv readme

[brettmc]

mention that tags align with the upstream semantic conventions repo

[codecov]

Codecov Report

Merging #1128 (c2f366a) into main (ea86fe1) will increase coverage by 0.78%.
Report is 1 commits behind head on main.
The diff coverage is n/a.

❗ Current head c2f366a differs from pull request most recent head 8a224d6. Consider uploading reports for the commit 8a224d6 to get more accurate results

@@             Coverage Diff              @@
##               main    #1128      +/-   ##
============================================
+ Coverage     83.50%   84.28%   +0.78%     
  Complexity     2160     2160              
============================================
  Files           279      279              
  Lines          6136     6136              
============================================
+ Hits           5124     5172      +48     
+ Misses         1012      964      -48     

Flag	Coverage Δ
7.4	82.91% <ø> (+0.78%)	⬆️
8.0	84.21% <ø> (+0.78%)	⬆️
8.1	84.35% <ø> (+0.78%)	⬆️
8.2	84.35% <ø> (+0.78%)	⬆️
8.3	84.35% <ø> (+0.78%)	⬆️

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see 8 files with indirect coverage changes

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