Fix remaining fx/all linux32 esr-next 404s

[janbrasna]

One-line summary

Skips ESR–next condition if linux i686, which no longer ships.

Significant changes and points to review

Porting mozmeao/springfield#1732

Issue / Bugzilla link

Fixes mozmeao/springfield#1726
Closes #17290 and also resolves #17284 now complete

Testing

http://localhost:8000/en-US/firefox/all/desktop-esr/linux/af/ (only single ESR, no 404)
http://localhost:8000/en-US/firefox/all/desktop-esr/linux64-aarch64/af/ (control, 2 ESRs)
http://localhost:8000/en-US/firefox/all/desktop-esr/win/af/ (control, 3 ESRs)

[codecov]

Codecov Report

❌ Patch coverage is 50.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 83.16%. Comparing base (025842d) to head (f8a2da9).

Files with missing lines	Patch %	Lines
bedrock/firefox/views.py	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #17362      +/-   ##
==========================================
- Coverage   83.17%   83.16%   -0.01%     
==========================================
  Files         180      180              
  Lines        9402     9404       +2     
==========================================
+ Hits         7820     7821       +1     
- Misses       1582     1583       +1     

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