reduce testing on travis, no macOS, no py3x-dev, see #5467 (1.1-maint)

[ThomasWaldmann]

• kill the macOS builds, way too expensive (and problematic anyway)
• kill the builds on python development versions, can't afford any more

[codecov-io]

Codecov Report

Merging #5471 into 1.1-maint will decrease coverage by 0.63%.
The diff coverage is n/a.

@@              Coverage Diff              @@
##           1.1-maint    #5471      +/-   ##
=============================================
- Coverage      80.07%   79.44%   -0.64%     
=============================================
  Files             27       27              
  Lines          10371    10371              
  Branches        1830     1830              
=============================================
- Hits            8305     8239      -66     
- Misses          1549     1610      +61     
- Partials         517      522       +5     

Impacted Files	Coverage Δ
src/borg/xattr.py	59.61% <0.00%> (-22.60%)	⬇️
src/borg/platform/__init__.py	73.68% <0.00%> (-15.79%)	⬇️
src/borg/platform/base.py	79.43% <0.00%> (-3.74%)	⬇️
src/borg/archive.py	80.81% <0.00%> (-0.90%)	⬇️
src/borg/helpers.py	88.15% <0.00%> (-0.37%)	⬇️
src/borg/repository.py	85.23% <0.00%> (-0.20%)	⬇️
src/borg/archiver.py	81.96% <0.00%> (+0.33%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 01d73e4...94f5e18. Read the comment docs.