playground: only pull nightly from cluster version

[xhebox]

What problem does this PR solve?

tiup playground v7.5.0 --tiproxy 1 will fail since bindVersion = "v7.5.0". We should only pull nightly instead.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

Code changes

• Has exported function/method change
• Has exported variable/fields change
• Has interface methods change
• Has persistent data change

Side effects

• Possible performance regression
• Increased code complexity
• Breaking backward compatibility

Related changes

• Need to cherry-pick to the release branch
• Need to update the documentation

Release notes:

NONE

[codecov-commenter]

Codecov Report

Attention: 3 lines in your changes are missing coverage. Please review.

Comparison is base (79c584f) 55.78% compared to head (22d4bbb) 54.51%.

❗ Current head 22d4bbb differs from pull request most recent head c5007e6. Consider uploading reports for the commit c5007e6 to get more accurate results

Files	Patch %	Lines
components/playground/playground.go	0.00%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2364      +/-   ##
==========================================
- Coverage   55.78%   54.51%   -1.27%     
==========================================
  Files         329      329              
  Lines       35024    35783     +759     
==========================================
- Hits        19537    19507      -30     
- Misses      13143    13940     +797     
+ Partials     2344     2336       -8     

Flag	Coverage Δ
playground	15.19% <0.00%> (-0.14%)	⬇️
tiup	33.60% <ø> (ø)
unittest	22.33% <0.00%> (+0.09%)	⬆️

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[kaaaaaaang]

/lgtm

[kaaaaaaang]

/approve

[ti-chi-bot]

@xhebox: Your PR was out of date, I have automatically updated it for you.

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[kaaaaaaang]

/lgtm

[kaaaaaaang]

/approve

[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-01-15 09:33:17.63350607 +0000 UTC m=+175639.197803760: ☑️ agreed by kaaaaaaang.
• 2024-01-15 13:49:53.966759728 +0000 UTC m=+191035.531057434: ✖️🔁 reset by xhebox.
• 2024-02-02 09:49:24.279926773 +0000 UTC m=+1731805.844224478: ☑️ agreed by kaaaaaaang.
• 2024-02-02 09:49:40.490085395 +0000 UTC m=+1731822.054383100: ✖️🔁 reset by ti-chi-bot[bot].
• 2024-02-02 09:54:45.232361872 +0000 UTC m=+1732126.796659579: ☑️ agreed by kaaaaaaang.

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: kaaaaaaang

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