improve ecosystem page

[qingyun-wu]

Why are these changes needed?

• Make the link to integration documentation more visible
• Remove duplicate example list
• Make citations consistent with that in arxiv

Related issue number

Checks

• I've included any doc changes needed for https://microsoft.github.io/autogen/. See https://microsoft.github.io/autogen/docs/Contribute#documentation to build and test documentation locally.
• I've added tests (if relevant) corresponding to the changes introduced in this PR.
• I've made sure all auto checks have passed.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (6f4d16e) 27.66% compared to head (62d851a) 27.66%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #823   +/-   ##
=======================================
  Coverage   27.66%   27.66%           
=======================================
  Files          27       27           
  Lines        3517     3517           
  Branches      801      801           
=======================================
  Hits          973      973           
  Misses       2473     2473           
  Partials       71       71           

Flag	Coverage Δ
unittests	27.60% <ø> (ø)

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