call signature escape characters moved from == to =`=, because that's something way less common.

test/signatures.vim

@@ -15,7 +15,7 @@ describe 'signatures'
         " equals doautocmd CursorMovedI
         Python jedi_vim.show_call_signatures()
 
-        Expect getline(1) == '==jedi=0, ==   (*number*) ==jedi=='
+        Expect getline(1) == '=`=jedi=0, =`=   (*number*) =`=jedi=`='
 
         doautocmd InsertLeave 
         Expect getline(1) == ''