Remove duplicate check for space character (32)

`_CharCode.SP` is 32, which is already covered by the `byte > 31` part.

Closes https://github.com/dart-lang/sdk/pull/40929
https://github.com/dart-lang/sdk/pull/40929

GitOrigin-RevId: bc2c0ea6d7e86a4a06135737da497f593ee9a03d
Change-Id: I5214775f76912e9985328f5c61b4a4ec4ef6b637
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/138787
Reviewed-by: Jonas Termansen <sortie@google.com>
Commit-Queue: Jonas Termansen <sortie@google.com>

sdk/lib/_http/http_parser.dart

@@ -978,7 +978,6 @@ class _HttpParser extends Stream<_HttpIncoming> {
 
   static bool _isValueChar(int byte) {
     return (byte > 31 && byte < 128) ||
-        (byte == _CharCode.SP) ||
         (byte == _CharCode.HT);
   }