Update dependency com.github.bitfireAT:dav4jvm to v2.2.1

Author: renovate[bot]

app/build.gradle

@@ -190,7 +190,7 @@ dependencies {
     implementation 'androidx.swiperefreshlayout:swiperefreshlayout:1.1.0'
     androidTestImplementation "androidx.work:work-testing:${workVersion}"
     implementation 'com.google.android.flexbox:flexbox:3.0.0'
-    implementation ('com.github.bitfireAT:dav4jvm:2.1.3', {
+    implementation ('com.github.bitfireAT:dav4jvm:2.2.1', {
         exclude group: 'org.ogce', module: 'xpp3'	// Android comes with its own XmlPullParser
     })
     implementation 'org.conscrypt:conscrypt-android:2.5.2'