C#: Delete the Internal StructuralComparisonConfiguration class as it is no longer needed.

csharp/ql/lib/semmle/code/csharp/commons/StructuralComparison.qll

@@ -236,55 +236,3 @@ abstract class StructuralComparisonConfiguration extends string {
    */
   predicate same(ControlFlowElement x, ControlFlowElement y) { candidate(x, y) and sameGvn(x, y) }
 }
-
-/**
- * INTERNAL: Do not use.
- *
- * A verbatim copy of the class `StructuralComparisonConfiguration` for internal
- * use.
- *
- * A copy is needed in order to use structural comparison within the standard
- * library without running into caching issues.
- */
-module Internal {
-  // Import all uses of the internal library to make sure caching works
-  private import semmle.code.csharp.controlflow.Guards as G
-
-  /**
-   * A configuration for performing structural comparisons of program elements
-   * (expressions and statements).
-   *
-   * The predicate `candidate()` must be overridden, in order to identify the
-   * elements for which to perform structural comparison.
-   *
-   * Each use of the library is identified by a unique string value.
-   */
-  abstract class InternalStructuralComparisonConfiguration extends string {
-    bindingset[this]
-    InternalStructuralComparisonConfiguration() { any() }
-
-    /**
-     * Holds if elements `x` and `y` are candidates for testing structural
-     * equality.
-     *
-     * Subclasses are expected to override this predicate to identify the
-     * top-level elements which they want to compare. Care should be
-     * taken to avoid identifying too many pairs of elements, as in general
-     * there are very many structurally equal subtrees in a program, and
-     * in order to keep the computation feasible we must focus attention.
-     *
-     * Note that this relation is not expected to be symmetric -- it's
-     * fine to include a pair `(x, y)` but not `(y, x)`.
-     * In fact, not including the symmetrically implied fact will save
-     * half the computation time on the structural comparison.
-     */
-    abstract predicate candidate(ControlFlowElement x, ControlFlowElement y);
-
-    /**
-     * Holds if elements `x` and `y` structurally equal. `x` and `y` must be
-     * flagged as candidates for structural equality, that is,
-     * `candidate(x, y)` must hold.
-     */
-    predicate same(ControlFlowElement x, ControlFlowElement y) { candidate(x, y) and sameGvn(x, y) }
-  }
-}