update ubuntu action runners

[dsabsay]

What this PR does:
Updates Ubuntu actions runners.

Which issue(s) this PR fixes:
Fixes #6582

Checklist

• Tests updated
• Documentation added
• CHANGELOG.md updated - the order of entries should be [CHANGE], [FEATURE], [ENHANCEMENT], [BUGFIX]

[dsabsay]

I'm guessing this is a flaky test:

--- FAIL: TestRing_ShuffleShard_Consistency (8.23s)
    --- FAIL: TestRing_ShuffleShard_Consistency/instances_=_20,_shard_size_=_12,_ring_operation_=_add-instance (0.27s)
        ring_test.go:1981: 
            	Error Trace:	/__w/cortex/cortex/pkg/ring/ring_test.go:1981
            	Error:      	"2" is not less than or equal to "1"
            	Test:       	TestRing_ShuffleShard_Consistency/instances_=_20,_shard_size_=_12,_ring_operation_=_add-instance
        ring_test.go:1982: 
            	Error Trace:	/__w/cortex/cortex/pkg/ring/ring_test.go:1982
            	Error:      	"2" is not less than or equal to "1"
            	Test:       	TestRing_ShuffleShard_Consistency/instances_=_20,_shard_size_=_12,_ring_operation_=_add-instance

[friedrichg]

thanks