Don't put the SMTP password into the HTML code

[nickvergessen]

Fix #4354

[mention-bot]

@nickvergessen, thanks for your PR! By analyzing the history of the files in this pull request, we identified @LukasReschke, @MorrisJobke and @schiessle to be potential reviewers.

[codecov]

Codecov Report

Merging #4372 into master will decrease coverage by 16.44%.
The diff coverage is 0%.

@@              Coverage Diff              @@
##             master    #4372       +/-   ##
=============================================
- Coverage     54.07%   37.63%   -16.45%     
- Complexity    21589    21591        +2     
=============================================
  Files          1327     1327               
  Lines         82303    82280       -23     
  Branches       1305     1305               
=============================================
- Hits          44509    30966    -13543     
- Misses        37794    51314    +13520

Impacted Files	Coverage Δ	Complexity Δ
lib/private/Settings/Admin/Additional.php	0% <0%> (-90.48%)	5 <0> (+1)
settings/templates/admin/additional-mail.php	0% <0%> (ø)	0 <0> (ø)	⬇️
settings/Controller/MailSettingsController.php	12.96% <0%> (-40.47%)	11 <0> (+1)
.../Exceptions/EncryptionHeaderKeyExistsException.php	0% <0%> (-100%)	1% <0%> (ø)
core/Command/TwoFactorAuth/Disable.php	0% <0%> (-100%)	4% <0%> (ø)
core/Command/TwoFactorAuth/Enable.php	0% <0%> (-100%)	4% <0%> (ø)
apps/user_ldap/lib/Settings/Section.php	0% <0%> (-100%)	5% <0%> (ø)
...curity/Exceptions/StrictCookieMissingException.php	0% <0%> (-100%)	1% <0%> (ø)
...factor_backupcodes/lib/Activity/GenericSetting.php	0% <0%> (-100%)	8% <0%> (ø)
apps/files/lib/Activity/Settings/FileChanged.php	0% <0%> (-100%)	8% <0%> (ø)
... and 445 more

[MorrisJobke]

Tested and works 👍

[MorrisJobke]

One ' was not replaced 🙈 (see #11218)