Add recent browser PR merges to release notes #3196

Job	Run time
test-current-cov (1.21.x, ubuntu-latest)	8m 18s
test-current-cov (1.21.x, windows-2019)	16m 2s
test-prev (1.20.x, ubuntu-latest)	1m 31s
test-current-cov (1.21.x, macos-latest)	5m 11s
test-prev (1.20.x, windows-2019)	6m 54s
test-prev (1.20.x, macos-latest)	7m 34s
test-tip (ubuntu-latest)	4m 31s
test-tip (windows-2019)	12m 40s
test-tip (macos-latest)	11m 4s
	1h 13m 45s

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