docs: nudge users into using partially encrypted config files

[aduh95]

With #1004 landed, it probably makes little sense for users to encrypt their entire config file, and instead only encrypt tokens. This PR updates the doc to remove mention of full config file encryption, and present token encryption as the default / recommended way for storing them.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.58%. Comparing base (7342aff) to head (9dc54d4).
⚠️ Report is 9 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1005      +/-   ##
==========================================
- Coverage   80.65%   80.58%   -0.08%     
==========================================
  Files          39       39              
  Lines        4746     4754       +8     
==========================================
+ Hits         3828     3831       +3     
- Misses        918      923       +5     

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[joyeecheung]

I think we should just split it into two different instructions with the encryption one prioritized as "Recommended". It's going to catch people off guard to recommend -x first only to come back with a note saying they should setup gpg first - that sounds like a pre-requisite that should be mentioned before we suggest the -x flag (and also, what if you don't have gpg set up? The doc provides no suggestions, and it is not great to leave new contributors guessing what they should do in that case when they are new to all this and are just trying to set it up).

[aduh95]

I've added "With encryption"/"Without encryption" variants, PTAL

[aduh95]

Ping @nodejs/node-core-utils for reviews