[gardening][Parse] Remove 2 unused flags in Parser (#4743)

* [Parse] Remove unused GreaterThanIsOperatorRAII. NFC

Last usage was removed in 68af974227.

* [Parse] Remove unused ArgumentIsParameter flag. NFC

Last usage was removed in 4e4173f2e6

include/swift/Parse/Parser.h

@@ -121,12 +121,6 @@ public:
     IVOLP_InLet
   } InVarOrLetPattern = IVOLP_NotInVarOrLet;
 
-  bool GreaterThanIsOperator = true;
-
-  /// FIXME: Temporary hack to keep the selector-style declaration
-  /// syntax working.
-  bool ArgumentIsParameter = false;
-
   bool InPoundLineEnvironment = false;
 
   LocalContext *CurLocalContext = nullptr;
@@ -222,24 +216,6 @@ public:
     }
   };
 
-  /// A RAII object for temporarily changing whether an operator starting with
-  /// '>' is an operator.
-  class GreaterThanIsOperatorRAII {
-    Parser &P;
-    bool OldValue;
-
-  public:
-    GreaterThanIsOperatorRAII(Parser &p, bool newValue)
-      : P(p), OldValue(p.GreaterThanIsOperator)
-    {
-      P.GreaterThanIsOperator = newValue;
-    }
-
-    ~GreaterThanIsOperatorRAII() {
-      P.GreaterThanIsOperator = OldValue;
-    }
-  };
-
   /// Describes the kind of a lexical structure marker, indicating
   /// what kind of structural element we started parsing at a
   /// particular location.