Provide only single targetSdkVersion build

Remove api19 build and default to api30 because we no longer access
files of other apps.

brouter-routing-app/build.gradle

@@ -17,6 +17,7 @@ android {
         setProperty("archivesBaseName", "BRouterApp." + defaultConfig.versionName)
 
         minSdkVersion 14
+        targetSdkVersion 30
 
         testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
     }
@@ -73,21 +74,6 @@ android {
         targetCompatibility JavaVersion.VERSION_1_8
     }
 
-
-    flavorDimensions "api"
-    productFlavors {
-        api19 {
-            dimension "api"
-
-            targetSdkVersion 19
-        }
-        api30 {
-            dimension "api"
-
-            targetSdkVersion 30
-        }
-    }
-
     applicationVariants.all {
         variant ->
             {