Turning off HMOVE display doesn't work in the new TIA core, and really was

only a hack in the old core.  We will eventually remove this.

src/emucore/tia/core_6502ts/TIA.cxx

@@ -723,13 +723,6 @@ bool TIA::toggleCollisions()
   return myCollisionsEnabledBits;
 }
 
-// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-// TODO: stub
-bool TIA::toggleHMOVEBlank()
-{
-  return false;
-}
-
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 // TODO: stub
 bool TIA::toggleFixedColors(uInt8 mode)

src/emucore/tia/core_6502ts/TIA.hxx

@@ -138,7 +138,8 @@ class TIA : public AbstractTIA
 
     bool toggleCollisions() override;
 
-    bool toggleHMOVEBlank() override;
+    // TODO - remove this completely, as it doesn't work in the new core
+    bool toggleHMOVEBlank() override { return true; }
 
     bool toggleFixedColors(uInt8 mode = 2) override;