Update build.gradle

[Muhriddin7675]

add namecpase

[RohitBaraiya]

add namecpase but still showing error

• What went wrong:
  A problem occurred configuring project ':flutter_barcode_scanner'.

Could not create an instance of type com.android.build.api.variant.impl.LibraryVariantBuilderImpl.
Namespace not specified. Specify a namespace in the module's build file. See https://d.android.com/r/tools/upgrade-assistant/set-namespace for information about setting the namespace.

please update lib