en, zh: Bump Operator to v1.2.0

[KanShiori]

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

Bump Operator to v1.2.0-rc.2

ref #1297
Run commands:

find . -type f | xargs sed -i "s/v1.2.0-rc.2/v1.2.0/g"

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

• master (the latest development version)
• v1.2 (TiDB Operator 1.2 versions)
• v1.1 (TiDB Operator 1.1 versions)
• v1.0 (TiDB Operator 1.0 versions)

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

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

Do your changes match any of the following descriptions?

• Delete files
• Change aliases
• Need modification after applied to another branch
• Might cause conflicts after applied to another branch

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• DanielZhangQD
• qiancai

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[DanielZhangQD]

LGTM

[qiancai]

LGTM

[qiancai]

/merge

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: d5b667f

[ti-chi-bot]

In response to a cherrypick label: new pull request created: #1339.