Issue 7972: sync the backupPVC deletion in expose clean up

[Lyndon-Li]

Fix issue #7972, sync the backupPVC deletion in expose clean up

[codecov]

Codecov Report

Attention: Patch coverage is 66.66667% with 3 lines in your changes missing coverage. Please review.

Project coverage is 58.84%. Comparing base (28d64c2) to head (7408dbd).
Report is 2 commits behind head on main.

Files	Patch %	Lines
pkg/exposer/generic_restore.go	0.00%	2 Missing ⚠️
pkg/exposer/csi_snapshot.go	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7973      +/-   ##
==========================================
+ Coverage   58.83%   58.84%   +0.01%     
==========================================
  Files         345      345              
  Lines       28795    28800       +5     
==========================================
+ Hits        16941    16947       +6     
+ Misses      10425    10424       -1     
  Partials     1429     1429              

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