Merge pull request #67 from embulk/upgrade-junit4-4.13.2-mockito-2.28.2

Upgrade JUnit 4 to 4.13.2 along with Mockito to 2.28.2

Author: dmikurube

gradle/libs.versions.toml

@@ -13,8 +13,8 @@ google-cloud-storage = "1.56.0"
 
 jcl-over-slf4j = "2.0.7"
 
-junit4 = "4.12"
-mockito = "2.18.3"
+junit4 = "4.13.2"
+mockito = "2.28.2"
 
 embulk-core = "0.11.4"
 embulk-formatter-csv = "0.10.36"