bazel: remove unnecessary build deps (grpc#12310)

Author: xuhongxu96

grpclb/BUILD.bazel

@@ -17,7 +17,6 @@ java_library(
         "//context",
         "//core:internal",
         "//stub",
-        "//util",
         "@com_google_protobuf//:protobuf_java_util",
         "@io_grpc_grpc_proto//:grpclb_load_balancer_java_proto",
         artifact("com.google.code.findbugs:jsr305"),

s2a/BUILD.bazel

@@ -57,7 +57,6 @@ java_library(
     ],
     deps = [
         ":token_manager",
-        ":s2a_channel_pool",
         ":s2a_identity",
         "//api",
         "//core:internal",

xds/BUILD.bazel

@@ -344,7 +344,6 @@ java_library(
         "//api",
         "//core:internal",
         "//stub",
-        "//testing",
         "//testing-proto:simpleservice_java_grpc",
         "//testing-proto:simpleservice_java_proto",
         "//util",