fix: Skip 32bit platform warning starting on 8.9 (#351)

As asnyc stack traces will not be turned on by default statring with node
8.9.0, The warning message of 'async stack trace is not available on 32 bit
platform' no longer emitted. We will not emit this elaboration to users.

test/test-debuglet.ts

@@ -345,7 +345,8 @@ describe('Debuglet', function() {
         // TODO: Handle the case where debuglet.debuggee is undefined
         assert.equal((debuglet.debuggee_ as Debuggee).project, projectId);
         const arch = process.arch;
-        if (semver.satisfies(process.version, '>=8.5') &&
+        if (semver.satisfies(process.version, '>=8.5.0') &&
+            semver.satisfies(process.version, '<8.9.0') &&
             (arch === 'ia32' || arch === 'x86') &&
             process.env.GCLOUD_USE_INSPECTOR) {
           assert(logText.includes(utils.messages.ASYNC_TRACES_WARNING));