message: Fix broken testing server in Java.
diff: @@ -27,6 +27,7 @@ java_library(
  "java/com/google/crypto/tink/testing/KeysetServiceImpl.java",
  "java/com/google/crypto/tink/testing/MacServiceImpl.java",
  "java/com/google/crypto/tink/testing/MetadataServiceImpl.java",
  + "java/com/google/crypto/tink/testing/PrfSetServiceImpl.java",
  "java/com/google/crypto/tink/testing/SignatureServiceImpl.java",
  "java/com/google/crypto/tink/testing/StreamingAeadServiceImpl.java",
  ],
  @@ -54,6 +55,7 @@ java_library(
  "@tink_java//src/main/java/com/google/crypto/tink:registry_cluster",
  "@tink_java//src/main/java/com/google/crypto/tink:streaming_aead",
  "@tink_java//src/main/java/com/google/crypto/tink:version",
  + "@tink_java//src/main/java/com/google/crypto/tink/prf:prf_set",
  ],
  )
  