Bump the minimum supported version of CodeQL to 2.15.5 #4076

Job	Run time
Go: tracing with autobuilder step (ubuntu-latest, stable-v2.15.5)	1m 14s
Go: tracing with autobuilder step (macos-latest, stable-v2.15.5)	2m 56s
Go: tracing with autobuilder step (ubuntu-latest, stable-v2.16.6)	1m 19s
Go: tracing with autobuilder step (macos-latest, stable-v2.16.6)	3m 46s
Go: tracing with autobuilder step (ubuntu-latest, stable-v2.17.6)	1m 19s
Go: tracing with autobuilder step (macos-latest, stable-v2.17.6)	3m 35s
Go: tracing with autobuilder step (ubuntu-latest, stable-v2.18.4)	1m 10s
Go: tracing with autobuilder step (macos-latest, stable-v2.18.4)	3m 32s
Go: tracing with autobuilder step (ubuntu-latest, stable-v2.19.4)	1m 20s
Go: tracing with autobuilder step (macos-latest, stable-v2.19.4)	3m 28s
Go: tracing with autobuilder step (ubuntu-latest, default)	52s
Go: tracing with autobuilder step (macos-latest, default)	3m 43s
Go: tracing with autobuilder step (ubuntu-latest, linked)	59s
Go: tracing with autobuilder step (macos-latest, linked)	3m 33s
Go: tracing with autobuilder step (ubuntu-latest, nightly-latest)	56s
Go: tracing with autobuilder step (macos-latest, nightly-latest)	4m 26s
	38m 8s

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