Add char static casts to crypto_utils_test.cc

When rolling quiche to Chromium, the compiler complains with narrowing
conversion error (-Wc++11-narrowing). Hence, this change adds static
casts to convert to char to silence this issue.

PiperOrigin-RevId: 494886209

quiche/quic/core/crypto/crypto_utils_test.cc

diff --git a/quiche/quic/core/crypto/crypto_utils_test.cc b/quiche/quic/core/crypto/crypto_utils_test.cc
index 505ee75..6bc17cf 100644
--- a/quiche/quic/core/crypto/crypto_utils_test.cc
+++ b/quiche/quic/core/crypto/crypto_utils_test.cc
@@ -209,7 +209,7 @@
                          0x7e,
                          0x37};
   const char v2_08_key[] = {// test vector from draft-ietf-quic-v2-08
-                            0x82,
+                            static_cast<char>(0x82),
                             static_cast<char>(0xdb),
                             static_cast<char>(0x63),
                             static_cast<char>(0x78),
@@ -222,8 +222,8 @@
                             0x19,
                             static_cast<char>(0xea),
                             0x71,
-                            0xd5,
-                            0xd2,
+                            static_cast<char>(0xd5),
+                            static_cast<char>(0xd2),
                             static_cast<char>(0xa7)};
   const char connection_id[] =  // test vector from both docs
       {static_cast<char>(0x83),