scheduler: use right check for evict/grant leader scheduler (#8758)

[ti-chi-bot]

This is an automated cherry-pick of #8758

What problem does this PR solve?

Issue Number: Ref #8756

What is changed and how does it work?

Check List

Tests

• Unit test
• Integration test

If I run the ut in release-7.1 branch, it will report error

--- FAIL: TestEvictLeaderScheduler (3.42s)
    /Users/jiangxianjie/Code/okjiang/pd/tests/pdctl/scheduler/scheduler_test.go:638: 
        	Error Trace:	/Users/jiangxianjie/Code/okjiang/pd/tests/pdctl/scheduler/scheduler_test.go:638
        	Error:      	"Failed! [400] \"[PD:scheduler:ErrSchedulerConfig]wrong scheduler config id\"\n\n" does not contain "Success!"
        	Test:       	TestEvictLeaderScheduler

Release note

Fix an issue that the grant/evict-leader-scheduler doesn't work when create them twice with the same store-id

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: okJiang, rleungx

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-11-05 08:43:12.294979241 +0000 UTC m=+944105.134134772: ☑️ agreed by okJiang.
• 2024-11-05 08:44:54.894630884 +0000 UTC m=+944207.733786429: ☑️ agreed by rleungx.