Add changelog entry for v3.28.20 backport #4480

Job	Run time
Diagnostic export (ubuntu-latest, linked)	59s
Diagnostic export (ubuntu-latest, nightly-latest)	1m 19s
Diagnostic export (windows-latest, linked)	1m 48s
Diagnostic export (macos-latest, nightly-latest)	2m 7s
Diagnostic export (macos-latest, linked)	1m 23s
Diagnostic export (windows-latest, nightly-latest)	3m 16s
	10m 52s

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