RemoveTestPrefix should also remove prefixes of implicitly referenced @MethodSource methods

[koppor]

When @MethodSource is hit, the referenced method should also be renamed

     @ParameterizedTest
     @MethodSource
-    void testContainsWhitespace(Boolean expected, String input) {
+    void containsWhitespace(Boolean expected, String input) {
        assertEquals(expected, StringUtil.containsWhitespace(input));
    }

That should also do

-    static Stream<Arguments> testContainsWhitespace() {
+    static Stream<Arguments> containsWhitespace() {

(but does not)

Relates to #258

[timtebeek]

Pushed up a small change to at least do no harm for now a426e40
We can keep this issue open for an improvement that also renames the implied method source, or introduces an explicitly named method source annotation argument.