bump minSdkVersion for screenshot tests

Signed-off-by: tobiasKaminsky <tobias@kaminsky.me>

build.gradle

@@ -156,6 +156,7 @@ android {
         buildTypes {
             debug {
                 testCoverageEnabled (project.hasProperty('coverage'))
+                minSdkVersion 21 // remove once we use 21 globally, only needed for karumi.shot
             }
         }