Fix typo and reword some explanations

Author: XiangRongLin

extractor/src/test/java/org/schabi/newpipe/MockOnly.java

@@ -9,7 +9,7 @@
 import javax.annotation.Nonnull;
 
 /**
- * Marker annotation to skip test if it not run with mocks.
+ * Marker annotation to skip test in certain cases.
  *
  * {@link MockOnlyRule}
  */
@@ -19,7 +19,7 @@
 public @interface MockOnly {
 
     /**
-     * Explanation why this test shold only be run with mocks and not against real websites
+     * Explanation why this test should be skipped
      */
     @Nonnull String reason();
 }

extractor/src/test/java/org/schabi/newpipe/MockOnlyRule.java

@@ -9,19 +9,21 @@
 import javax.annotation.Nonnull;
 
 /**
+ *
  * <p>
- * Checks if the system variable "downloader" is set to "REAL" and skips the tests if it is.
- * Otherwise execute the test.
+ * Allows skipping unreliable or time sensitive tests in CI pipeline.
  * </p>
  *
  * <p>
  * Use it by creating a public variable of this inside the test class and annotate it with
- * {@link org.junit.Rule}. Then annotate the tests to be skipped with {@link MockOnly}
+ * {@link org.junit.Rule}. Then annotate the specific tests to be skipped with {@link MockOnly}
  * </p>
  *
  * <p>
- * Allows skipping unreliable or time sensitive tests in CI pipeline.
+ * It works by checking if the system variable "downloader" is set to "REAL" and skips the tests if it is.
+ * Otherwise it executes the test.
  * </p>
+
  */
 public class MockOnlyRule implements TestRule {
 
@@ -42,7 +44,6 @@ public void evaluate() throws Throwable {
                             + annotation.reason(), isMockDownloader);
                 }
 
-
                 base.evaluate();
             }
         };