Auto merge of #29638 - mrobinson:fix-notify, r=mukilan

Make errors during build status notification warnings

Instead of raising an exception, simply print a warning on stderr when notification fails.

Fixes #29635.

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- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix #29635
- [x] These changes do not require tests because they fix a minor tools issue.

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