Update TestEtcdHealthyWithTinySnapshotCatchupEntries to mitigate the context timeout flaky

[ahrtr]

Reduce the concurrency and requests to mitigate the flaky.

    etcd_config_test.go:631: 
        	Error Trace:	/home/prow/go/src/github.com/etcd-io/etcd/tests/e2e/etcd_config_test.go:631
        	Error:      	Received unexpected error:
        	            	match not found.  Set EXPECT_DEBUG for more info Errs: [unexpected exit code [1] after running [/home/prow/go/src/github.com/etcd-io/etcd/bin/etcdctl --endpoints=http://localhost:20000,http://localhost:20005,http://localhost:20010 put foo bar3 -w json]], last lines:
        	            	{"level":"warn","ts":"2026-06-18T21:03:38.007703Z","logger":"etcd-client","caller":"v3/retry_interceptor.go:68","msg":"retrying of unary invoker failed","target":"etcd-endpoints://0x2293b651c00/localhost:20000","peer":"Peer{Addr: '127.0.0.1:20000', LocalAddr: '127.0.0.1:39852', AuthInfo: 'insecure'}","method":"/etcdserverpb.KV/Put","attempt":0,"error":"rpc error: code = DeadlineExceeded desc = context deadline exceeded"}
        	            	Error: context deadline exceeded
        	Test:       	TestEtcdHealthyWithTinySnapshotCatchupEntries

https://prow.k8s.io/view/gs/kubernetes-ci-logs/pr-logs/pull/etcd-io_etcd/21978/pull-etcd-e2e-amd64/2067711287218933760

https://prow.k8s.io/view/gs/kubernetes-ci-logs/pr-logs/pull/etcd-io_etcd/21978/pull-etcd-e2e-arm64/2067711287298625536

cc @fuweid @ivanvc @serathius

[k8s-ci-robot]

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[ahrtr]

/retest

[k8s-ci-robot]

@ahrtr: The following tests failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
pull-etcd-govulncheck	cf4b6fc	link	true	/test pull-etcd-govulncheck
pull-etcd-e2e-amd64	cf4b6fc	link	true	/test pull-etcd-e2e-amd64

Full PR test history. Your PR dashboard. Please help us cut down on flakes by linking to an open issue when you hit one in your PR.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 69.71%. Comparing base (5f6496a) to head (9e2679e).
⚠️ Report is 21 commits behind head on main.

Additional details and impacted files

see 23 files with indirect coverage changes

@@            Coverage Diff             @@
##             main   #21979      +/-   ##
==========================================
- Coverage   69.79%   69.71%   -0.08%     
==========================================
  Files         449      449              
  Lines       38163    38163              
==========================================
- Hits        26634    26607      -27     
- Misses      10102    10130      +28     
+ Partials     1427     1426       -1     

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[serathius]

https://gist.github.com/liggitt/6a3a2217fa5f846b52519acfc0ffece0

[henrybear327]

Linking prior attempt: #21924

[kubernetes-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: ahrtr

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The pull request process is described here

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Needs approval from an approver in each of these files:

• OWNERS [ahrtr]

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[ahrtr]

The test case is just flaky, sometimes it timeouts.

cc @fuweid @serathius

[ahrtr]

/retest