Fix compiler warning issues in fizz/server/ServerProtocol.cpp

Summary:
This diff fixes issues identified by one or more of these compiler warning flags:
* `-Wpessimizing-move`
* `-Wmissing-braces `
* `-Wself-assign`
* `-Wunused-lambda-capture `
* `-Wheader-hygiene`
* `-Wunused-variable`
* `-Wunused-parameter`
* `-Wsign-compare`

If the code compiles, it should work.

Reviewed By: dmm-fb

Differential Revision: D52970480

fbshipit-source-id: 172f2cfb79af4018444d379937682d9cbbfc402e

fizz/server/ServerProtocol.cpp

@@ -690,7 +690,7 @@ static void validateGroups(const std::vector<KeyShareEntry>& client_shares) {
 }
 
 static std::tuple<NamedGroup, Optional<Buf>> negotiateGroup(
-    ProtocolVersion version,
+    ProtocolVersion /*version*/,
     const ClientHello& chlo,
     const std::vector<NamedGroup>& supportedGroups) {
   auto groups = getExtension<SupportedGroups>(chlo.extensions);
@@ -747,7 +747,7 @@ static HelloRetryRequest getHelloRetryRequest(
     CipherSuite cipher,
     NamedGroup group,
     Buf legacySessionId,
-    HandshakeContext& handshakeContext) {
+    HandshakeContext& /*handshakeContext*/) {
   HelloRetryRequest hrr;
   hrr.legacy_version = ProtocolVersion::tls_1_2;
   hrr.legacy_session_id_echo = std::move(legacySessionId);