SbatLevel_Variable.txt: clarify where and how revocation data is tracked #959

Job	Run time
f41 x64 build compile_commands.json	2m 53s
f41 x64 build	2m 7s
f41 aa64 cross-build	2m 3s
f40 x64 build	1m 58s
f40 aa64 cross-build	2m 1s
f39 x64 build	1m 56s
f41 arm cross-build	1m 59s
centos9 x64 build	1m 9s
f40 arm cross-build	2m 7s
centos8 x64 build	1m 13s
f39 arm cross-build	1m 53s
f39 ia32 build	1m 56s
f41 x64 cross-build	2m 11s
centos8 ia32 build	1m 14s
f40 x64 cross-build	2m 11s
f39 x64 cross-build	1m 54s
f41 ia32 cross-build	2m 3s
f40 ia32 cross-build	1m 58s
f39 ia32 cross-build	1m 54s
	36m 40s

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