ci: remove unmaintained, inactive gpu-tests stack (#48166) #1

Job	Run time
changes	29s
prechecks / bootstrap-dev-rhel8	5m 13s
prechecks / style	59s
prechecks / pylint	56s
prechecks / import-check	2m 41s
prechecks / validate	35s
prechecks / audit / package-audits (windows-latest, powershell Invoke-Expression -Command "./share/spack/qa/windows_t...	4m 58s
prechecks / audit / package-audits (ubuntu-latest, bash)	8m 39s
prechecks / audit / package-audits (macos-latest, bash)	5m 38s
all-prechecks	1s
unit-tests	0s
bootstrap	0s
coverage	0s
all	2s
	30m 11s

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