Fix unreachable-return issue in folly/IPAddress.cpp +1

Summary:
LLVM has a warning `-Wunreachable-code-return` which we treat as an error because the condition it flags compromises readability. This diff fixes related issues by removing unreachable returns.

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Reviewed By: dtolnay

Differential Revision: D76478022

fbshipit-source-id: 7070b82fc7b050cbd1971ca18f7926be77eb0502

Author: r-barnes

third-party/folly/src/folly/IPAddress.cpp

@@ -133,8 +133,6 @@ CIDRNetwork IPAddress::createNetwork(
   }
 
   CHECK(0);
-
-  return CIDRNetwork{};
 }
 
 // public static