[BUILD] Change repositories mode when using gradle init scripts

[anuragmantri]

Polaris uses RepositoriesMode.FAIL_ON_PROJECT_REPOS setting for dependency management. For companies using gradle init scripts with internal repository declarations, this will fail to build with below error

Build was configured to prefer settings repositories over project repositories but repository 'maven' was added by initialization script '/Users/anurag/.gradle/init.gradle' 

Should we remove this mode or set it to PREFER_SETTINGS instead?

What are your thoughts @flyrain @aihuaxu ?

[flyrain]

I'm OK with that, as it will make it easy for companies to integrate with internal libs. Feel free to file an PR. Also, this property is introduced by #53, cc @snazy for that.

[snazy]

I'm okay to remove the setting (use the default).