Replace EasyMock dependency with Mockito and re-pin Bazel deps

protobuf_deps.bzl

diff --git a/protobuf_deps.bzl b/protobuf_deps.bzl
index 27b8bee..2bee1b7 100644
--- a/protobuf_deps.bzl
+++ b/protobuf_deps.bzl
@@ -11,7 +11,7 @@
     "com.google.guava:guava-testlib:30.1.1-jre",
     "com.google.truth:truth:1.1.2",
     "junit:junit:4.12",
-    "org.easymock:easymock:3.2",
+    "org.mockito:mockito-core:4.3.1",
 ]
 
 def protobuf_deps():