Clear cache according to https://www.scala-sbt.org/1.x/docs/Travis-CI-with-sbt.html#Caching

Author: Atry

.travis.yml

@@ -14,8 +14,9 @@ jdk:
   - openjdk11
 
 before_cache:
-  - find $HOME/.sbt -name '*.lock' -delete
-  - find $HOME/.ivy2 -name 'ivydata-*.properties' -delete
+  - rm -fv $HOME/.ivy2/.sbt.ivy.lock
+  - find $HOME/.ivy2/cache -name "ivydata-*.properties" -print -delete
+  - find $HOME/.sbt        -name "*.lock"               -print -delete
 
 cache:
   directories: