fix retrofit to 2.6.x

build.gradle

@@ -66,12 +66,10 @@ dependencies {
     implementation 'org.conscrypt:conscrypt-android:2.2.1'
     implementation 'me.drakeet.support:toastcompat:1.1.0'
     implementation "com.leinardi.android:speed-dial:2.0.1"
-    implementation("com.squareup.retrofit2:retrofit:2.7.1") {
-        exclude group: "com.squareup.okhttp3", "module": "okhttp"
-    }
-    implementation("com.squareup.retrofit2:converter-gson:2.7.1") {
-        exclude group: "com.squareup.okhttp3", "module": "okhttp"
-    }
+    //retrofit needs to stick with 2.6.x (https://github.com/square/retrofit/blob/master/CHANGELOG.md)
+    implementation "com.squareup.retrofit2:retrofit:2.6.4"
+    implementation "com.squareup.retrofit2:converter-gson:2.6.4"
+    //okhttp needs to stick with 3.12.x
     implementation 'com.squareup.okhttp3:okhttp:3.12.7'
     implementation 'com.google.guava:guava:27.1-android'
     quicksyImplementation 'io.michaelrocks:libphonenumber-android:8.11.1'