Auto merge of #5922 - bundler:colby/fix-new-init-env-var, r=indirect
Auto merge of #5922 - bundler:colby/fix-new-init-env-var, r=indirect

fix documented init gems rb config env var

### What was the end-user problem that led to this PR?

I documented the env var for the init new gem file feature flag incorrectly

### What was your diagnosis of the problem?

    › BUNDLE_NEW_GEMFILE_NAME=1 dbundler init
    Writing new Gemfile to /Users/c/Desktop/Projects/testapp/Gemfile

does not generate the gems.rb as expected

### What is your fix for the problem, implemented in this PR?

Use the correct env name to generate gems.rb

dilumnavanjana/bundler,bundler/bundler,dilumnavanjana/bundler,mvz/bundler,bundler/bundler,mvz/bundler