Update sbt-scalafix and sbt versions

[travisbrown]

Like #3210 but doesn't fail.

I've seen this error in other contexts from sbt 1.3.5:

[error] java.lang.NoClassDefFoundError: org/scalacheck/Test$TestCallback
[error] 	at java.lang.Class.getDeclaredFields0(Native Method)
[error] 	at java.lang.Class.privateGetDeclaredFields(Class.java:2583)
[error] 	at java.lang.Class.getDeclaredFields(Class.java:1916)

…and I'm pretty sure it has something to do with having both ScalaCheck 1.13 and 1.14 dependencies around (in this case via the old scalafix-testkit's dependency on some weird ScalaTest 3.2 version). In any case updating Scalafix seems to fix the issue.

[codecov-io]

Codecov Report

Merging #3212 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #3212   +/-   ##
=======================================
  Coverage   93.05%   93.05%           
=======================================
  Files         376      376           
  Lines        7412     7412           
  Branches      192      192           
=======================================
  Hits         6897     6897           
  Misses        515      515

Flag	Coverage Δ
#scala_version_212	93.38% <ø> (ø)	⬆️
#scala_version_213	92.82% <ø> (ø)	⬆️

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