remove e2e slow tag for VolumeSubpathEnvExpansion

Kubernetes e2e suite: [It] [sig-node] Variable Expansion should fail
substituting values in a volume subpath with absolute path [Slow]
[Conformance] test takes 37 seconds to run

Author: aojea

test/conformance/testdata/conformance.yaml

@@ -2656,7 +2656,7 @@
   file: test/e2e/common/node/expansion.go
 - testname: VolumeSubpathEnvExpansion, subpath with absolute path
   codename: '[sig-node] Variable Expansion should fail substituting values in a volume
-    subpath with absolute path [Slow] [Conformance]'
+    subpath with absolute path [Conformance]'
   description: Make sure a container's subpath can not be set using an expansion of
     environment variables when absolute path is supplied.
   release: v1.19

test/e2e/common/node/expansion.go

@@ -187,7 +187,7 @@ var _ = SIGDescribe("Variable Expansion", func() {
 		Testname: VolumeSubpathEnvExpansion, subpath with absolute path
 		Description: Make sure a container's subpath can not be set using an expansion of environment variables when absolute path is supplied.
 	*/
-	framework.ConformanceIt("should fail substituting values in a volume subpath with absolute path", f.WithSlow(), func(ctx context.Context) {
+	framework.ConformanceIt("should fail substituting values in a volume subpath with absolute path", func(ctx context.Context) {
 		absolutePath := "/tmp"
 		if framework.NodeOSDistroIs("windows") {
 			// Windows does not typically have a C:\tmp folder.