Fix typo in doc (https://velero.io/docs/main/restore-reference/ "Restore order" section)

[niulechuan]

Please add a summary of your change

Fix typo in doc (https://velero.io/docs/main/restore-reference/ "Restore order" section),
"Mamespace" should be "Namespace".

Does your change fix a particular issue?

None

Fixes #(issue)

Please indicate you've done the following:

• Accepted the DCO. Commits without the DCO will delay acceptance.
• Created a changelog file or added /kind changelog-not-required as a comment on this pull request.
• Updated the corresponding documentation in site/content/docs/main.

[codecov-commenter]

Codecov Report

Merging #5051 (c6625d1) into main (ec5503f) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #5051   +/-   ##
=======================================
  Coverage   41.30%   41.30%           
=======================================
  Files         210      210           
  Lines       18439    18439           
=======================================
  Hits         7616     7616           
  Misses      10253    10253           
  Partials      570      570           

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