JavaScript: Make File not extend Locatable anymore.

Files have strange `:0:0:0:0` locations for... reasons. This makes the predicates inherited from `Locatable` meaningless. A particularly bad case is `getNumLines()`, which will always return one. The right predicate to use is, of course, `getNumberOfLines()`, which is defined in `File` itself.

Author: Max Schaefer

javascript/ql/src/semmle/javascript/Files.qll

@@ -198,8 +198,8 @@ class Folder extends Container, @folder {
 }
 
 /** A file. */
-class File extends Container, @file, Locatable {
-  override Location getLocation() { hasLocation(this, result) }
+class File extends Container, @file {
+  Location getLocation() { hasLocation(this, result) }
 
   override string getAbsolutePath() { files(this, result, _, _, _) }