only build one android apk on Travis

follow-up 0333632eb0

.travis.yml

@@ -58,6 +58,8 @@ jobs:
       name: "Android build"
       language: python
       python: 3.7
+      env:
+        - CI=true
       services:
         - docker
       install:

electrum/gui/kivy/Readme.md

@@ -67,7 +67,7 @@ You probably need to clear the cache: `rm -rf .buildozer/android/platform/build/
 ### How do I deploy on connected phone for quick testing?
 Assuming `adb` is installed:
 ```
-$ adb -d install -r bin/Electrum-*-debug.apk
+$ adb -d install -r bin/Electrum-*-arm64-v8a-debug.apk
 $ adb shell monkey -p org.electrum.electrum 1
 ```