Revert "IRGen: Deserialize SIL witness tables and shared-linkage definitions by need."

include/swift/SIL/SILModule.h

@@ -715,11 +715,6 @@ public:
   bool isDefaultAtomic() const {
     return ! getOptions().AssumeSingleThreaded;
   }
-  
-  /// Returns true if SIL entities associated with declarations in the given
-  /// declaration context ought to be serialized as part of this module.
-  bool shouldSerializeEntitiesAssociatedWithDeclContext(const DeclContext *DC)
-    const;
 };
 
 inline llvm::raw_ostream &operator<<(llvm::raw_ostream &OS, const SILModule &M){