change getSplitAt to getSeparator

Co-authored-by: Esben Sparre Andreasen <[email protected]>

Author: erik-krogh

javascript/ql/src/semmle/javascript/StandardLibrary.qll

@@ -162,7 +162,7 @@ class StringSplitCall extends DataFlow::MethodCallNode {
   /**
    * Gets a string that determines where the string is split.
    */
-  string getSplitAt() {
+  string getSeparator() {
     getArgument(0).mayHaveStringValue(result)
     or
     result =