Fix https probe after 8.9.1 revert

As the previous change was reverted, and won't go into the 8.x release
line, we only need to do this for 9.0.0 and up.

Refs: nodejs/node#16660

probes/https-outbound-probe.js

@@ -25,8 +25,8 @@ var util = require('util');
 var semver = require('semver');
 
 var methods;
-// In Node.js < v8.9.0 'get' calls 'request' so we only instrument 'request'
-if (semver.lt(process.version, '8.9.0')) {
+// In Node.js < v9.0.0 'get' calls 'request' so we only instrument 'request'
+if (semver.lt(process.version, '9.0.0')) {
   methods = ['request'];
 } else {
   methods = ['request', 'get'];