common: remove unused MapStringStructToSlice

It's unused since commit c49ef45 ("metrics: Modularize daemon
metrics registry").

In case similar functionality is needed in the future, the generic
functions in the standard library maps package or in
golang.org/x/exp/maps should be used.

Signed-off-by: Tobias Klauser <tobias@cilium.io>

pkg/common/utils.go

@@ -74,13 +74,3 @@ func RequireRootPrivilege(cmd string) {
 		os.Exit(1)
 	}
 }
-
-// MapStringStructToSlice returns a slice with all keys of the given
-// map[string]struct{}
-func MapStringStructToSlice(m map[string]struct{}) []string {
-	s := make([]string, 0, len(m))
-	for k := range m {
-		s = append(s, k)
-	}
-	return s
-}