JS: Remove unused isInPlainCodeContext

Author: asgerf

javascript/ql/src/semmle/javascript/frameworks/Templating.qll

@@ -116,12 +116,6 @@ module Templating {
       not getRawText().regexpMatch("(?s)\\{\\{.*\\}\\}")
     }
 
-    /**
-     * Holds if this occurs in generated code as an expression or statement,
-     * that is, without being enclosed in a string literal or similar.
-     */
-    predicate isInPlainCodeContext() { this = any(GeneratedCodeExpr e).getPlaceholderTag() }
-
     /**
      * Gets the innermost JavaScript expression containing this template tag, if any.
      */