Update test to use proper step pattern.

Found by CodeRabbit:

Line 625 has an undefined step: `${TEST_NAMESPACE}` does not match the registered
step pattern.

The step definition for "with needed permissions" is registered only for the
literal in test namespace pattern (verified in test/e2e/steps/steps.go line 128).
Line 625 uses `in ${TEST_NAMESPACE}`, which will cause the e2e test to fail with
an undefined step error. Update it to match the registered pattern.

Signed-off-by: Todd Short <tshort@redhat.com>

Author: tmshort

test/e2e/features/install.feature

@@ -622,7 +622,7 @@ Feature: Install ClusterExtension
       """
       Verbs:[create]
       """
-    When ServiceAccount "olm-sa" with needed permissions is available in ${TEST_NAMESPACE}
+    When ServiceAccount "olm-sa" with needed permissions is available in test namespace
     Then ClusterExtension is available
     And ClusterExtension reports Progressing as True with Reason Succeeded
     And ClusterExtension reports Installed as True