KAFKA-19635: Minor docs tweaks (#20434)

Improve the wording in the upgrade doc slightly. Also fix a tiny
annoyance in the output from the message generator.

Reviewers: Apoorv Mittal <[email protected]>

Author: AndrewJSchofield

docs/upgrade.html

@@ -74,8 +74,8 @@ <h5><a id="upgrade_420_notable" href="#upgrade_420_notable">Notable changes in 4
                         <code>kafka-producer-perf-test.sh</code> (<code>--producer-props</code> is deprecated in favor of <code>--command-property</code>)
                     </li>
                     <li>
-                        <code>kafka-consumer-perf-test.sh</code> and <code>kafka-share-consumer-perf-test.sh</code> gain
-                        <code>--command-property</code> to bring all performance testing tools in line
+                        <code>kafka-consumer-perf-test.sh</code> and <code>kafka-share-consumer-perf-test.sh</code> gain the
+                        <code>--command-property</code> option to bring all performance testing tools in line
                     </li>
                 </ul>
             </li>

generator/src/main/java/org/apache/kafka/message/MessageGenerator.java

@@ -269,7 +269,7 @@ public static void processDirectories(String packageName,
                 }
             }
         }
-        System.out.printf("MessageGenerator: processed %d Kafka message JSON files(s).%n", numProcessed);
+        System.out.printf("MessageGenerator: processed %d Kafka message JSON file(s).%n", numProcessed);
     }
 
     /**