apply review comment concerning targetSdkVersion

https://github.com/owncloud/android-library/pull/198#discussion_r228050760

sample_client/AndroidManifest.xml

@@ -29,9 +29,6 @@
           android:versionName="1.0">
 
     <uses-permission android:name="android.permission.INTERNET"/>
-    <uses-sdk
-        android:minSdkVersion="14"
-        android:targetSdkVersion="26"/>
     <application
         android:icon="@drawable/ic_launcher"
         android:label="@string/app_name">

sample_client/build.gradle

@@ -11,6 +11,11 @@ dependencies {
 android {
     compileSdkVersion 26
 
+    defaultConfig {
+        minSdkVersion 14
+        targetSdkVersion 26
+    }
+
     sourceSets {
         main {
             manifest.srcFile 'AndroidManifest.xml'