e2e framework: don't add default skip when --label-filter is used

The new pull-kubernetes-kind-dra uses
    -label-filter='Feature: containsAny DynamicResourceAllocation && !Flaky && !Serial'
to run DRA tests. That didn't work because the E2E framework behind its back
added the default skip expression.

test/e2e/framework/test_context.go

@@ -399,7 +399,7 @@ func CreateGinkgoConfig() (types.SuiteConfig, types.ReporterConfig) {
 	// Randomize specs as well as suites
 	suiteConfig.RandomizeAllSpecs = true
 	// Disable skipped tests unless they are explicitly requested.
-	if len(suiteConfig.FocusStrings) == 0 && len(suiteConfig.SkipStrings) == 0 {
+	if len(suiteConfig.FocusStrings) == 0 && len(suiteConfig.SkipStrings) == 0 && suiteConfig.LabelFilter == "" {
 		suiteConfig.SkipStrings = []string{`\[Flaky\]|\[Feature:.+\]`}
 	}
 	return suiteConfig, reporterConfig