docs: fix tls customisation minVersion case

[Dean-Coakley]

What type of PR is this?

What this PR does / why we need it:

• Without it the tls minVersion spec does not cleanly apply when applying from a file

Error from server (BadRequest): error when creating "custom.yaml": EnvoyProxy in version "v1alpha1" cannot be handled as a EnvoyProxy: strict decoding error: unknown field "spec.backendTLS.MinVersion"

Which issue(s) this PR fixes:

Fixes #

Release Notes: Yes/No

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 70.50%. Comparing base (845b36b) to head (a43c5d8).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6212      +/-   ##
==========================================
+ Coverage   70.46%   70.50%   +0.03%     
==========================================
  Files         220      220              
  Lines       36593    36593              
==========================================
+ Hits        25787    25800      +13     
+ Misses       9281     9271      -10     
+ Partials     1525     1522       -3     

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[arkodg]

LGTM thanks !

[zirain]

please fix DCO