src: remove validation of unreachable code

Based on nodejs/help#2600 (comment)
the condition (amount < 0) won't be possible.

PR-URL: #32818
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Yongsheng Zhang <zyszys98@gmail.com>
Reviewed-By: Zeyu Yang <himself65@outlook.com>
Reviewed-By: Shelley Vohr <codebytere@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Gus Caplan <me@gus.host>

src/node_os.cc

@@ -137,16 +137,12 @@ static void GetCPUInfo(const FunctionCallbackInfo<Value>& args) {
 
 static void GetFreeMemory(const FunctionCallbackInfo<Value>& args) {
   double amount = uv_get_free_memory();
-  if (amount < 0)
-    return;
   args.GetReturnValue().Set(amount);
 }
 
 
 static void GetTotalMemory(const FunctionCallbackInfo<Value>& args) {
   double amount = uv_get_total_memory();
-  if (amount < 0)
-    return;
   args.GetReturnValue().Set(amount);
 }