Fix comment from #158719 (#159157)

Author: hjyamauchi

llvm/lib/Support/Windows/Program.inc

@@ -220,8 +220,7 @@ static bool Execute(ProcessInfo &PI, StringRef Program,
       llvm::append_range(EnvBlock, EnvString);
       EnvBlock.push_back(0);
     }
-    // If an empty environment (*Env is size zero), we need to
-    // terminate with two nulls.
+    // Empty environments need to be terminated with two nulls.
     if (Env->size() == 0)
       EnvBlock.push_back(0);
     EnvBlock.push_back(0);