Delete docs-update.yml

[chalin]

Together with open-telemetry/opentelemetry.io#804, this closes #423. The docs-update workflow is no longer relevant.

/cc @austinlparker

[codecov]

Codecov Report

Merging #435 (c9394f1) into main (b5a8952) will not change coverage.
The diff coverage is n/a.

❗ Current head c9394f1 differs from pull request most recent head b4f780a. Consider uploading reports for the commit b4f780a to get more accurate results

@@            Coverage Diff            @@
##               main     #435   +/-   ##
=========================================
  Coverage     92.04%   92.04%           
  Complexity      793      793           
=========================================
  Files            65       65           
  Lines          1961     1961           
=========================================
  Hits           1805     1805           
  Misses          156      156           

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