Update lines mentioning Mollie in docs

[whyscream]

Just noted that the Mollie backend was added to the docs, thank you for that :)
Some slight changes to the information listed.

[codecov]

Codecov Report

Merging #366 (bdd9cc4) into main (8737608) will decrease coverage by 0.32%.
Report is 1 commits behind head on main.
The diff coverage is 73.38%.

@@            Coverage Diff             @@
##             main     #366      +/-   ##
==========================================
- Coverage   79.30%   78.99%   -0.32%     
==========================================
  Files          28       29       +1     
  Lines        1899     1947      +48     
  Branches      235      241       +6     
==========================================
+ Hits         1506     1538      +32     
- Misses        276      293      +17     
+ Partials      117      116       -1     

Files Changed	Coverage Δ
payments/stripe/forms.py	93.58% <ø> (-0.17%)	⬇️
payments/stripe/providers.py	72.99% <72.99%> (ø)
payments/stripe/__init__.py	67.30% <100.00%> (-5.36%)	⬇️

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[WhyNotHugo]

Thanks