Merge pull request NativeScript#1927 from AdamAtri/patch-2

docs: Update e2e testing overview.md

Author: NathanaelA

docs/tooling/testing/end-to-end-testing/overview.md

@@ -37,7 +37,7 @@ For the plugin to work correctly you need to have:
 
 * Install Appium globally:
 ```shell
-$ npm install -g appium
+$ npm install -g appium@1.18.1
 ```
 
 * iOS Dependencies