gitlab-ci: set Fedora build to use a supported build-tools version

gitlab-ci: set Fedora build to use a supported build-tools version

Using 25.0.2, not all of the permissions were being output:

--- /builds/fdroid/fdroidserver/tests/repo/index.xml	2017-12-28 22:33:53.624704459 +0000
+++ repo/index.xml	2017-12-28 22:41:52.207849097 +0000
@@ -35,7 +35,6 @@
 			<added>2017-12-22</added>
 			<sig>2d337e40aef77564bf62781ac424595c</sig>
 			<permissions>ACCESS_NETWORK_STATE,ACCESS_WIFI_STATE,CHANGE_WIFI_MULTICAST_STATE,INTERNET,READ_EXTERNAL_STORAGE,WRITE_EXTERNAL_STORAGE</permissions>
-			<uses-permission maxSdkVersion="18" name="android.permission.READ_EXTERNAL_STORAGE"/>
 			<uses-permission maxSdkVersion="18" name="android.permission.WRITE_EXTERNAL_STORAGE"/>
 			<uses-permission-sdk-23 maxSdkVersion="27" name="android.permission.REQUEST_IGNORE_BATTERY_OPTIMIZATIONS"/>
 		</package>