Remove warning about signing GitHub OIDC Tokens being experimental #283

Job	Run time
Install Cosign v0.6.0 and test presence in path with pre installed libpcsclite1 package (ubuntu-l...	16s
Install Cosign and test presence in path (macos-latest)	12s
Install Cosign and test presence in path (ubuntu-latest)	5s
Install Cosign and test presence in path (windows-latest)	15s
Install Custom Cosign and test presence in path (macos-latest)	16s
Install Custom Cosign and test presence in path (ubuntu-latest)	6s
Install Custom Cosign and test presence in path (windows-latest)	20s
Install Cosign v0.6.0 and test presence in path (macos-latest)	18s
Install Cosign v0.6.0 and test presence in path (ubuntu-latest)	23s
Install Cosign v0.6.0 and test presence in path (windows-latest)	26s
Install Custom Cosign and test presence in path (macos-latest)	11s
Install Custom Cosign and test presence in path (ubuntu-latest)	6s
Install Custom Cosign and test presence in path (windows-latest)	17s
Try to install a wrong Cosign (macos-latest)	11s
Try to install a wrong Cosign (ubuntu-latest)	3s
Try to install a wrong Cosign (windows-latest)	14s
Install Custom Cosign and test presence in path with custom root dir (ubuntu-latest)	6s
Try to install cosign with go 1.19	3m 56s
Try to install cosign with go 1.20	4m 2s
Try to install cosign with go 1.19	3m 13s
Try to install cosign with go 1.20	2m 55s
Try to install cosign with go 1.19	9m 33s
Try to install cosign with go 1.20	11m 20s
Install existing release of Cosign and test presence in path (ubuntu-latest)	5s
	38m 49s

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