Bump Android NDK to r17b (#20357)

Summary:
This PR bumps Android NDK version to r17b (latest). Cleaned up redundant **LOCAL_EXPORT_CPPFLAGS** rules in .mk files
Pull Request resolved: facebook/react-native#20357

Differential Revision: D9068424

Pulled By: hramos

fbshipit-source-id: 8578637e38e807288b819a36cb75ea9feefcc09f

templates/HelloWorld/android/gradle.properties

@@ -16,5 +16,3 @@
 # This option should only be used with decoupled projects. More details, visit
 # http://www.gradle.org/docs/current/userguide/multi_project_builds.html#sec:decoupled_projects
 # org.gradle.parallel=true
-
-android.useDeprecatedNdk=true