fix #8821 JS codegen can produce extreme switch statements with case … (#20548)

* fix #8821 JS codegen can produce extreme switch statements with case a of range

* remove totalRange

tests/js/t8821.nim

@@ -1,6 +1,3 @@
-discard """
-  errormsg: "Your case statement contains too many branches, consider using if/else instead!"
-"""
 
 proc isInt32(i: int): bool =
   case i 
@@ -9,4 +6,4 @@ proc isInt32(i: int): bool =
   else:
     return false
 
-discard isInt32(1)
+doAssert isInt32(1) == true