bump extractor version

Author: erik-krogh

javascript/extractor/src/com/semmle/js/extractor/Main.java

@@ -43,7 +43,7 @@ public class Main {
    * A version identifier that should be updated every time the extractor changes in such a way that
    * it may produce different tuples for the same file under the same {@link ExtractorConfig}.
    */
-  public static final String EXTRACTOR_VERSION = "2020-04-01";
+  public static final String EXTRACTOR_VERSION = "2020-08-18";
 
   public static final Pattern NEWLINE = Pattern.compile("\n");