Remove TimeUtil.java and TimeUtilTest.java from Makefile.am (#8750)

This should fix the failing distcheck test.

Makefile.am

diff --git a/Makefile.am b/Makefile.am
index 573003b..c1c98a4 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -578,7 +578,6 @@
   java/util/src/main/java/com/google/protobuf/util/FieldMaskTree.java              \
   java/util/src/main/java/com/google/protobuf/util/FieldMaskUtil.java              \
   java/util/src/main/java/com/google/protobuf/util/JsonFormat.java                 \
-  java/util/src/main/java/com/google/protobuf/util/TimeUtil.java                   \
   java/util/src/main/java/com/google/protobuf/util/Structs.java                    \
   java/util/src/main/java/com/google/protobuf/util/Timestamps.java                 \
   java/util/src/main/java/com/google/protobuf/util/Values.java                     \
@@ -586,7 +585,6 @@
   java/util/src/test/java/com/google/protobuf/util/FieldMaskUtilTest.java          \
   java/util/src/test/java/com/google/protobuf/util/JsonFormatTest.java             \
   java/util/src/test/java/com/google/protobuf/util/StructsTest.java                \
-  java/util/src/test/java/com/google/protobuf/util/TimeUtilTest.java               \
   java/util/src/test/java/com/google/protobuf/util/ValuesTest.java                 \
   java/util/src/test/proto/com/google/protobuf/util/json_test.proto