Spurious quote mark in command line when typing <C-R> (#9934)

Remove <C-R> special char after reading following chars

src/nvim/ex_getln.c

@@ -1389,6 +1389,7 @@ static int command_line_handle_key(CommandLineState *s)
         }
       }
     }
+    ccline.special_char = NUL;
     redrawcmd();
     return command_line_changed(s);
 

test/functional/ui/cmdline_highlight_spec.lua

@@ -983,7 +983,7 @@ describe('Expressions coloring support', function()
       {EOB:~                                       }|
       {EOB:~                                       }|
       {EOB:~                                       }|
-      ={SQ:"}{SB:<c0>}{SQ:"}{E:<c0>"}{SB:foo}{E:"}^"                       |
+      ={SQ:"}{SB:<c0>}{SQ:"}{E:<c0>"}{SB:foo}{E:"}^                        |
     ]])
   end)
 end)