Remove trivially-true check in parsed_cookie.cc

IsControlCharacter() was checking an unsigned char to
make sure it's >= 0, which is trivially true. This throws
a warning on the default CrOS toolchain, so remove it even though it's harmless

BUG=424334
TEST=net_unittests
R=rsleevi@chromium.org

Review URL: https://codereview.chromium.org/640303008

Cr-Commit-Position: refs/heads/master@{#300170}

net/cookies/parsed_cookie.cc

@@ -137,7 +137,7 @@ bool IsValidCookieValue(const std::string& value) {
 }
 
 bool IsControlCharacter(unsigned char c) {
-    return (c >= 0) && (c <= 31);
+  return c <= 31;
 }
 
 bool IsValidCookieAttributeValue(const std::string& value) {