chore: use hosted httpbin in e2e tests

[jonas-jonas]

This should deflake the e2e tests a bit.

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
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  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 #3422 (dc9ddd7) into master (ce8139f) will decrease coverage by 0.01%.
Report is 1 commits behind head on master.
The diff coverage is n/a.

❗ Current head dc9ddd7 differs from pull request most recent head 65afa36. Consider uploading reports for the commit 65afa36 to get more accurate results

@@            Coverage Diff             @@
##           master    #3422      +/-   ##
==========================================
- Coverage   78.04%   78.03%   -0.01%     
==========================================
  Files         327      327              
  Lines       21384    21379       -5     
==========================================
- Hits        16689    16684       -5     
  Misses       3457     3457              
  Partials     1238     1238              

see 1 file with indirect coverage changes