docs(guide): clarify login limits

[jsjoeio]

Changes wording around login limits to prevent confusion: #3979

Fixes N/A

[codecov]

Codecov Report

Merging #4040 (f2bef94) into main (c913386) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #4040   +/-   ##
=======================================
  Coverage   63.51%   63.51%           
=======================================
  Files          36       36           
  Lines        1872     1872           
  Branches      379      379           
=======================================
  Hits         1189     1189           
  Misses        580      580           
  Partials      103      103           

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[github-actions]

✨ Coder.com for PR #4040 deployed! It will be updated on every commit.

• Host: https://codercom-ecivkznsv-codercom.vercel.app/docs/code-server
• Last deploy status: success
• Commit: f2bef94
• Workflow status: https://github.com/cdr/code-server/actions/runs/1167572672