Bump Android Gradle PLugin to 7.0.4

Signed-off-by: Álvaro Brey Vilas <alvaro.brey@nextcloud.com>

build.gradle

@@ -19,7 +19,7 @@ buildscript {
         mavenCentral()
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:7.0.3'
+        classpath 'com.android.tools.build:gradle:7.0.4'
         classpath 'com.hiya:jacoco-android:0.2'
         classpath 'com.github.spotbugs.snom:spotbugs-gradle-plugin:4.8.0'
         classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"