Remove powermock test reference

Java 11 powermock fails due to a requirement for a Java XML module.
Test is not valuable enough to wrestle with the mocking framework.
Remove the test, replace it later or confirm that the case is already
covered elsewhere in JenkinsRule based tests.

Author: MarkEWaite

pom.xml

@@ -139,16 +139,6 @@
       <artifactId>mockito-core</artifactId>
       <scope>test</scope>
     </dependency>
-    <dependency>
-      <groupId>org.powermock</groupId>
-      <artifactId>powermock-module-junit4</artifactId>
-      <scope>test</scope>
-    </dependency>
-    <dependency>
-      <groupId>org.powermock</groupId>
-      <artifactId>powermock-api-mockito2</artifactId>
-      <scope>test</scope>
-    </dependency>
     <dependency>
       <groupId>nl.jqno.equalsverifier</groupId>
       <artifactId>equalsverifier</artifactId>

src/test/java/jenkins/plugins/git/AbstractGitSCMSourceRetrieveHeadsTest.java

@@ -52,7 +52,6 @@
 import java.util.Iterator;
 import java.util.List;
 import java.util.Set;
-import static jenkins.plugins.git.AbstractGitSCMSourceRetrieveHeadsTest.EXPECTED_GIT_EXE;
 import jenkins.plugins.git.traits.GitBrowserSCMSourceTrait;
 import jenkins.plugins.git.traits.GitToolSCMSourceTrait;
 import jenkins.scm.api.SCMFileSystem;
@@ -555,7 +554,7 @@ public AbstractGitSCMSourceImpl() {
         @NonNull
         @Override
         public List<SCMSourceTrait> getTraits() {
-            return Collections.<SCMSourceTrait>singletonList(new GitToolSCMSourceTrait(EXPECTED_GIT_EXE) {
+            return Collections.<SCMSourceTrait>singletonList(new GitToolSCMSourceTrait("git-custom") {
                 @Override
                 public SCMSourceTraitDescriptor getDescriptor() {
                     return new GitBrowserSCMSourceTrait.DescriptorImpl();