Min SDK version should be removed from Manifest templates

Otherwise the following error comes up during compilation of sketch:

```
 Failed to parse XML in /private/var/folders/dl/6khbyrbx22vfbf2s_yjt1zx80000gs/T/android14837169316708129763sketch/app/src/main/AndroidManifest.xml
  The minSdk version should not be declared in the android manifest file. You can move the version from the manifest to the defaultConfig in the build.gradle file.
```