Updated a comment on LookUpConformance to reflect current implementation

LookUpConformance does not depend on a type checker instance anymore.

Author: gribozavr

lib/Sema/TypeChecker.h

@@ -1054,8 +1054,7 @@ class TypeChecker final {
                      SourceLoc ComplainLoc = SourceLoc());
 
   /// Functor class suitable for use as a \c LookupConformanceFn to look up a
-  /// conformance through a particular declaration context using the given
-  /// type checker.
+  /// conformance through a particular declaration context.
   class LookUpConformance {
     DeclContext *dc;