ci(circleci): speed up dev_mac job

[lahabana]

Summary

Remove parallelism limit on dev_mac job which likely slowed down the whole build
Tests of this showed tests taking about half the time it does currently.

[codecov-commenter]

Codecov Report

Merging #3665 (63638bd) into master (999b7a8) will increase coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #3665      +/-   ##
==========================================
+ Coverage   50.90%   50.91%   +0.01%     
==========================================
  Files         927      927              
  Lines       56508    56508              
==========================================
+ Hits        28766    28773       +7     
+ Misses      25453    25440      -13     
- Partials     2289     2295       +6     

Impacted Files	Coverage Δ
pkg/plugins/leader/postgres/leader_elector.go	93.61% <0.00%> (-6.39%)	⬇️
pkg/xds/cache/once/cache.go	82.05% <0.00%> (-5.13%)	⬇️
pkg/xds/cache/once/once.go	95.00% <0.00%> (-5.00%)	⬇️
pkg/defaults/components.go	86.95% <0.00%> (-4.35%)	⬇️
pkg/core/resources/manager/cache.go	83.11% <0.00%> (-2.60%)	⬇️
pkg/insights/resyncer.go	73.61% <0.00%> (+2.45%)	⬆️
pkg/events/eventbus.go	92.59% <0.00%> (+7.40%)	⬆️
pkg/core/runtime/component/component.go	88.67% <0.00%> (+7.54%)	⬆️
pkg/insights/components.go	100.00% <0.00%> (+30.00%)	⬆️

---

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 999b7a8...63638bd. Read the comment docs.

[jakubdyszkiewicz]

good find!