JS: Bump extractor version string

Author: asgerf

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

@@ -38,7 +38,7 @@ 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 = "2020-02-14";
+  public static final String EXTRACTOR_VERSION = "2020-04-01";
 
   public static final Pattern NEWLINE = Pattern.compile("\n");