Move the annotation to the same package

Javadoc explains the difference between this one and the testing-advice-ones enough, and "generated" was questionable

Author: Maria Kusber

src/main/java/com/diffblue/cover/annotations/generated/MethodsUnderTest.java renamed to src/main/java/com/diffblue/cover/annotations/MethodsUnderTest.java

@@ -12,7 +12,7 @@
  * express or implied. See the License for the specific language governing
  * permissions and limitations under the License.
  */
-package com.diffblue.cover.annotations.generated;
+package com.diffblue.cover.annotations;
 
 import static java.lang.annotation.ElementType.METHOD;
 import static java.lang.annotation.RetentionPolicy.SOURCE;