Fix GTEST_OS_ESP8266 check

Everywhere else in the code, we check the value of GTEST_OS_ESP8266, not just
whether it is defined.

PiperOrigin-RevId: 499946909
Change-Id: I86f7e8947abb4e928fc24d1416d8237987b27845

googletest/src/gtest.cc

@@ -5030,7 +5030,7 @@ class ScopedPrematureExitFile {
   }
 
   ~ScopedPrematureExitFile() {
-#if !defined GTEST_OS_ESP8266
+#if !GTEST_OS_ESP8266
     if (!premature_exit_filepath_.empty()) {
       int retval = remove(premature_exit_filepath_.c_str());
       if (retval) {