Test flake: `TestSortLabelsAndMatchers_Selectors`

[seizethedave]

--- FAIL: TestSortLabelsAndMatchers_Selectors (0.02s)
    --- FAIL: TestSortLabelsAndMatchers_Selectors/metric{namespace="1",_namespace!="2",_namespace=~"3",_namespace!~"5",_namespace!~"4",_namespace=~"6",_namespace!="7",_namespace="8"} (0.01s)
        sort_labels_and_matchers_test.go:165: 
            	Error Trace:	/__w/mimir/mimir/pkg/streamingpromql/optimize/ast/sort_labels_and_matchers_test.go:165
            	            				/__w/mimir/mimir/pkg/streamingpromql/optimize/ast/sort_labels_and_matchers_test.go:172
            	Error:      	Not equal: 
            	            	expected: &parser.VectorSelector{Name:"metric", OriginalOffset:0, Offset:0, Timestamp:(*int64)(nil), SkipHistogramBuckets:false, StartOrEnd:0, LabelMatchers:[]*labels.Matcher{(*labels.Matcher)(0xc0002c7ec0), (*labels.Matcher)(0xc0002c7ef0), (*labels.Matcher)(0xc0002c7f20), (*labels.Matcher)(0xc0002c7f50), (*labels.Matcher)(0xc0002ea000), (*labels.Matcher)(0xc0002ea030), (*labels.Matcher)(0xc0002ea120), (*labels.Matcher)(0xc0002ea150), (*labels.Matcher)(0xc0002ea180)}, UnexpandedSeriesSet:storage.SeriesSet(nil), Series:[]storage.Series(nil), BypassEmptyMatcherCheck:false, PosRange:posrange.PositionRange{Start:0, End:132}}
            	            	actual  : &parser.VectorSelector{Name:"metric", OriginalOffset:0, Offset:0, Timestamp:(*int64)(nil), SkipHistogramBuckets:false, StartOrEnd:0, LabelMatchers:[]*labels.Matcher{(*labels.Matcher)(0xc0002ea4e0), (*labels.Matcher)(0xc0002ea330), (*labels.Matcher)(0xc0002ea4b0), (*labels.Matcher)(0xc0002ea360), (*labels.Matcher)(0xc0002ea480), (*labels.Matcher)(0xc0002ea3[90](https://github.com/grafana/mimir/actions/runs/14322484837/job/40141949644#step:8:91)), (*labels.Matcher)(0xc0002ea420), (*labels.Matcher)(0xc0002ea3f0), (*labels.Matcher)(0xc0002ea3c0)}, UnexpandedSeriesSet:storage.SeriesSet(nil), Series:[]storage.Series(nil), BypassEmptyMatcherCheck:false, PosRange:posrange.PositionRange{Start:0, End:132}}

action log

[charleskorn]

I'm not able to reproduce the flakiness, but #11149 should make it easier to understand flakes in the future if they do occur.