docs: clarify supported deployment strategies

[johnmwood]

The current concept docs seem to suggest that Recreate and RollingUpdate deployment strategies are supported by Argo Rollouts:

To make it clear how the Argo Rollouts will behave, here are the descriptions of the various deployment strategies implementations offered by the Argo Rollouts.

I changed the wording in this PR to make the supported APIs more clear. This line caused some confusion on our end because we believed that users had the option to use Recreate or RollingUpdate strategies and we wanted to reject any Rollout admissions with those strategies.

Checklist:

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[github-actions]

Published E2E Test Results

  4 files    4 suites   3h 14m 45s ⏱️
113 tests 103 ✅  7 💤 3 ❌
458 runs  424 ✅ 28 💤 6 ❌

For more details on these failures, see this check.

Results for commit a1f8988.

♻️ This comment has been updated with latest results.

[github-actions]

Published Unit Test Results

2 275 tests   2 275 ✅  2m 58s ⏱️
  128 suites      0 💤
    1 files        0 ❌

Results for commit a1f8988.

♻️ This comment has been updated with latest results.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 83.86%. Comparing base (ff93786) to head (a1f8988).
Report is 3 commits behind head on master.

Additional details and impacted files

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##           master    #3823   +/-   ##
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  Coverage   83.86%   83.86%           
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  Files         163      163           
  Lines       18560    18560           
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  Hits        15565    15565           
  Misses       2121     2121           
  Partials      874      874           

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[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

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