Chore: update labels of travis builds (NativeScript#207)

.travis.yml

@@ -108,7 +108,7 @@ matrix:
         - "curl -u $SAUCE_USER:$SAUCE_KEY -X POST -H 'Content-Type: application/octet-stream' $SAUCE_STORAGE/$ANDROID_PACKAGE_NG?overwrite=true --data-binary @$ANDROID_PACKAGE_FOLDER_NG/app-debug.apk"
     - stage: "UI Tests"
       env:
-        - Android="24"
+        - Android="28"
         - Type="VanillaJS"
       language: node_js
       os: linux
@@ -119,7 +119,7 @@ matrix:
         - travis_wait travis_retry npm run e2e -- --runType android28 --sauceLab --appPath $ANDROID_PACKAGE_JS
     - os: linux
       env:
-        - Android="24"
+        - Android="28"
         - Type="VueJS"
       language: node_js
       os: linux
@@ -150,7 +150,7 @@ matrix:
         - travis_wait travis_retry npm run e2e -- --runType sim12iPhoneX --sauceLab --appPath $IOS_PACKAGE_VUE
     - os: linux
       env:
-        - Android="24"
+        - Android="28"
         - Type="Angular"
       language: node_js
       os: linux