Bump protobuf-java from 2.6.1 to 3.21.4 in /java#64

dependabot[bot] wants to merge 1 commit intomastermoazreyad/singa:masterfrom

b0dfdependabot/maven/java/com.google.protobuf-protobuf-java-3.21.4moazreyad/singa:b0dfdependabot/maven/java/com.google.protobuf-protobuf-java-3.21.4Copy head branch name to clipboard