Try to use ruby 2.7 for CI

[johnynek]

try to fix #1100

[codecov-commenter]

Codecov Report

Base: 89.60% // Head: 89.66% // Increases project coverage by +0.05% 🎉

Coverage data is based on head (72f7114) compared to base (3cefba6).
Patch has no changes to coverable lines.

❗ Current head 72f7114 differs from pull request most recent head 129e643. Consider uploading reports for the commit 129e643 to get more accurate results

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1101      +/-   ##
===========================================
+ Coverage    89.60%   89.66%   +0.05%     
===========================================
  Files          119      124       +5     
  Lines        10016    10050      +34     
  Branches       695      695              
===========================================
+ Hits          8975     9011      +36     
+ Misses        1041     1039       -2     

Impacted Files	Coverage Δ
.../main/scala/com/twitter/algebird/Successible.scala	87.50% <0.00%> (-4.17%)	⬇️
.../main/scala/com/twitter/algebird/BloomFilter.scala	93.50% <0.00%> (-0.87%)	⬇️
.../scala/com/twitter/algebird/immutable/BitSet.scala	96.64% <0.00%> (-0.42%)	⬇️
...main/scala-2.12-/com/twitter/algebird/compat.scala	83.33% <0.00%> (ø)
...-2.12-/com/twitter/algebird/immutable/compat.scala	80.00% <0.00%> (ø)
.../scala/com/twitter/algebird/MetricProperties.scala	100.00% <0.00%> (ø)
....12-/com/twitter/algebird/macros/MacroCompat.scala	60.00% <0.00%> (ø)
....12-/com/twitter/algebird/collections/compat.scala	100.00% <0.00%> (ø)
...src/main/scala/com/twitter/algebird/Interval.scala	80.95% <0.00%> (+4.76%)	⬆️
...scala/com/twitter/algebird/CorrelationMonoid.scala	94.11% <0.00%> (+7.35%)	⬆️

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

☔ View full report at Codecov.
📢 Do you have feedback about the report comment? Let us know in this issue.