fix: send out correct verification invalid email in code strategy

[jonas-jonas]

Fixes wrong email templates used when sending the "invalid" verification via code email and adds some tests to detect these issues in the future.

Related issue(s)

Checklist

• I have read the contributing guidelines.
• I have referenced an issue containing the design document if my change
  introduces a new feature.
• I am following the
  contributing code guidelines.
• I have read the security policy.
• I confirm that this pull request does not address a security
  vulnerability. If this pull request addresses a security vulnerability, I
  confirm that I got the approval (please contact
  security@ory.sh) from the maintainers to push
  the changes.
• I have added tests that prove my fix is effective or that my feature
  works.
• I have added or changed the documentation.

Further Comments

[codecov]

Codecov Report

Merging #2908 (5b16e46) into master (e1119e8) will not change coverage.
The diff coverage is 50.00%.

@@           Coverage Diff           @@
##           master    #2908   +/-   ##
=======================================
  Coverage   76.12%   76.12%           
=======================================
  Files         308      308           
  Lines       18887    18887           
=======================================
  Hits        14378    14378           
  Misses       3390     3390           
  Partials     1119     1119           

Impacted Files	Coverage Δ
selfservice/strategy/code/code_sender.go	78.07% <50.00%> (ø)

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