gradle: replace use of obsolete 'compile' configuration. (#532)

'compile' is obsolete and has been replaced with 'implementation' and 'api'.

Signed-off-by: ardevd <edvard.holst@gmail.com>

app/build.gradle

@@ -146,7 +146,7 @@ dependencies {
     implementation ('com.gitlab.bitfireAT:dav4jvm:f2078bc846', {
         exclude group: 'org.ogce', module: 'xpp3'	// Android comes with its own XmlPullParser
     })
-    compile 'org.conscrypt:conscrypt-android:2.0.0'
+    implementation 'org.conscrypt:conscrypt-android:2.0.0'
 
 
     implementation 'androidx.lifecycle:lifecycle-extensions:2.0.0'