[NFC] clean-up collectExistentialConformances

Author: kavon

include/swift/AST/Module.h

@@ -853,8 +853,10 @@ class ModuleDecl
   ProtocolConformanceRef conformsToProtocol(Type sourceTy,
                                             ProtocolDecl *targetProtocol);
 
-  /// Collect the conformances of \c fromType each of the protocols of an
+  /// Collect the conformances of \c fromType to each of the protocols of an
   /// existential type's layout.
+  ///
+  /// See `TypeChecker::containsProtocol` for details on the boolean arguments.
   ArrayRef<ProtocolConformanceRef>
   collectExistentialConformances(CanType fromType, CanType existential,
                                  bool skipConditionalRequirements = true,

include/swift/AST/TypeCheckRequests.h

@@ -345,10 +345,6 @@ class CollectExistentialConformancesRequest
                CanType existential,
                bool skipConditionalRequirements,
                bool allowMissing) const;
-
-public:
-  // Caching.
-  bool isCached() const { return true; }
 };
 
 /// Determine whether an existential type conforming to this protocol