Clean and optimize CI

[alexandrebouthinon]

What does this PR do?

• Remove MacOS and Windows 32bit jobs
• Tests only latest Go version
• Use YAML anchors
• Disable success notifications

[codecov[bot]]

Codecov Report

Merging #254 into 2-dev will decrease coverage by 0.04%. The diff coverage is n/a.

@@            Coverage Diff             @@
##            2-dev     #254      +/-   ##
==========================================
- Coverage   88.91%   88.87%   -0.05%     
==========================================
  Files         244      244              
  Lines        4466     4466              
==========================================
- Hits         3971     3969       -2     
- Misses        441      443       +2     
  Partials       54       54

Impacted Files	Coverage Δ
realtime/subscribe.go	70.58% <0%> (-5.89%)	:arrow_down:

---

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 084a6c0...977be0b. Read the comment docs.

[codecov[bot]]

Codecov Report

Merging #254 into 2-dev will decrease coverage by 0.04%. The diff coverage is n/a.

@@            Coverage Diff             @@
##            2-dev     #254      +/-   ##
==========================================
- Coverage   88.91%   88.87%   -0.05%     
==========================================
  Files         244      244              
  Lines        4466     4466              
==========================================
- Hits         3971     3969       -2     
- Misses        441      443       +2     
  Partials       54       54

Impacted Files	Coverage Δ
realtime/subscribe.go	70.58% <0%> (-5.89%)	:arrow_down:

---

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 084a6c0...3e7e289. Read the comment docs.