Remove email configuration

[stonezdj]

Email related settings are deprecated
Remove email ping API
Fixes #17683

Signed-off-by: stonezdj stonezdj@gmail.com

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Comprehensive Summary of your change

Issue being fixed

Fixes #(issue)

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[codecov]

Codecov Report

Merging #17712 (7fa7247) into main (0acfbdc) will decrease coverage by 0.03%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main   #17712      +/-   ##
==========================================
- Coverage   66.60%   66.57%   -0.04%     
==========================================
  Files         995      994       -1     
  Lines      105898   105673     -225     
  Branches     2602     2602              
==========================================
- Hits        70536    70347     -189     
+ Misses      31464    31425      -39     
- Partials     3898     3901       +3     

Flag	Coverage Δ
unittests	66.57% <ø> (-0.04%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/lib/config/models/model.go	100.00% <ø> (ø)
src/lib/config/userconfig.go	68.27% <ø> (-1.29%)	⬇️
...g-retention-tasks/tag-retention-tasks.component.ts	61.11% <0.00%> (-25.00%)	⬇️
src/common/rbac/system/namespace.go	35.29% <0.00%> (-11.77%)	⬇️
src/core/auth/authenticator.go	48.81% <0.00%> (-9.45%)	⬇️
src/common/utils/passports.go	86.27% <0.00%> (-3.93%)	⬇️
src/common/utils/email/mail.go	35.05% <0.00%> (-3.10%)	⬇️
src/server/v2.0/restapi/embedded_spec.go	100.00% <0.00%> (ø)
src/portal/src/app/shared/units/shared.utils.ts	36.47% <0.00%> (+2.35%)	⬆️
...es/vulnerability/vulnerability-config.component.ts	62.96% <0.00%> (+4.44%)	⬆️
... and 3 more

[chlins]

lgtm