src: remove unprofessional slang in assertions

Convert `CHECK(0 && "wtf?")` (sic) assertions to more suitable
`UNREACHABLE()` macro invocations in `node_zlib.cc`.

PR-URL: #17166
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Timothy Gu <timothygu99@gmail.com>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Daniel Bevenius <daniel.bevenius@gmail.com>
Reviewed-By: Anatoli Papirovski <apapirovski@mac.com>

src/node_zlib.cc

@@ -336,7 +336,7 @@ class ZCtx : public AsyncWrap {
         }
         break;
       default:
-        CHECK(0 && "wtf?");
+        UNREACHABLE();
     }
 
     // pass any errors back to the main thread to deal with.
@@ -547,7 +547,7 @@ class ZCtx : public AsyncWrap {
             ->AdjustAmountOfExternalAllocatedMemory(kInflateContextSize);
         break;
       default:
-        CHECK(0 && "wtf?");
+        UNREACHABLE();
     }
 
     ctx->dictionary_ = reinterpret_cast<Bytef *>(dictionary);