fix the configuration format in multiple disks mounting

[Oreoxmt]

What is changed, added, or deleted? (Required)

Close https://github.com/pingcap/docs-tidb-operator/issues/2398

Which TiDB Operator version(s) do your changes apply to? (Required)

• [x] master (the latest development version)
• [x] v1.5 (TiDB Operator 1.5 versions)
• [x] v1.4 (TiDB Operator 1.4 versions)
• [x] v1.3 (TiDB Operator 1.3 versions)
• [x] v1.2 (TiDB Operator 1.2 versions)

What is the related PR or file link(s)?

• This PR is translated from:
• Other reference link(s):

[Oreoxmt]

@csuzhangxc PTAL

[ti-chi-bot[bot]]

[LGTM Timeline notifier]

Timeline:

• 2023-07-04 02:26:15.379609241 +0000 UTC m=+84407.313242656: :ballot_box_with_check: agreed by csuzhangxc.

[Oreoxmt]

/approve

[ti-chi-bot[bot]]

[APPROVALNOTIFIER] This PR is APPROVED

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[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-1.2: #2400.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-1.3: #2401.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-1.4: #2402.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-1.5: #2403.