docs: make external-dns example to 0.7.2+ working in AWS China

[zxkane]

external-dns supports AWS China since 0.7.2, it also requires additional endpoints permission

[k8s-ci-robot]

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[codecov-io]

Codecov Report

Merging #1680 (68dfa11) into main (fbbeffc) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #1680   +/-   ##
=======================================
  Coverage   46.11%   46.11%           
=======================================
  Files         110      110           
  Lines        5920     5920           
=======================================
  Hits         2730     2730           
  Misses       2926     2926           
  Partials      264      264           

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[M00nF1sh]

/lgtm
thanks for contributing 👍