Update dependencies (#87)

gradle/libs.versions.toml

@@ -3,6 +3,7 @@ assertj = "3.25.1"
 cel = "0.4.3"
 ipaddress = "5.4.0"
 junit = "5.10.1"
+maven-publish = "0.27.0"
 # When updating, make sure to update buf.gen.yaml and src/test/resources/proto/buf.gen.*.yaml versions to match
 # and regenerate code with 'make generate'.
 protobuf = "3.25.1"
@@ -16,14 +17,12 @@ guava = { module = "com.google.guava:guava", version = "33.0.0-jre" }
 ipaddress = { module = "com.github.seancfoley:ipaddress", version.ref = "ipaddress" }
 jakarta-mail-api = { module = "jakarta.mail:jakarta.mail-api", version = "2.1.2" }
 junit-bom = { module = "org.junit:junit-bom", version.ref = "junit" }
-maven-plugin = { module = "com.vanniktech:gradle-maven-publish-plugin", version = "0.27.0" }
-mail = { module = "javax.mail:mail", version = "1.4.7"}
+maven-plugin = { module = "com.vanniktech:gradle-maven-publish-plugin", version.ref = "maven-publish" }
 nullaway = { module = "com.uber.nullaway:nullaway", version = "0.10.19" }
 protobuf-java = { module = "com.google.protobuf:protobuf-java", version.ref = "protobuf" }
-protobuf-java-util = { module = "com.google.protobuf:protobuf-java-util", version.ref = "protobuf" }
 spotless = { module = "com.diffplug.spotless:spotless-plugin-gradle", version = "6.23.3" }
 
 [plugins]
 errorprone = { id = "net.ltgt.errorprone", version = "3.1.0" }
 git = { id = "com.palantir.git-version", version = "3.0.0" }
-maven = { id = "com.vanniktech.maven.publish.base", version = "0.27.0" }
+maven = { id = "com.vanniktech.maven.publish.base", version.ref = "maven-publish" }