Cherry pick PR #1854: Edit headings of cobalt/site/docs files for DevSite migration #1131

Job	Run time
stub / initialize	32s
stub / docker-build-image	32s
stub / docker-unittest-image	0s
stub / stub_devel	5m 11s
stub / stub_debug	5m 31s
stub / stub_qa	4m 42s
stub / stub_gold	4m 19s
stub / ${{ matrix.name }}_${{ matrix.shard }}_test	0s
stub / ${{ matrix.name }}_on_device_${{ matrix.shard }}	0s
stub / on-host-unit-test-report	0s
	20m 47s

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