Update .gitignore (#3708)

Accidentally updated the file while doing 8.13.48 release.

Reverting the file to reflect old changes from https://github.com/google/libphonenumber/pull/3640/files

.gitignore

@@ -1,14 +1,5 @@
-# Ignore build directories and any files generated by the update script.
-cpp/build/
-cpp/src/phonenumbers/geocoding/geocoding_data.cc
-cpp/src/phonenumbers/phonemetadata.pb.*
-cpp/src/phonenumbers/phonenumber.pb.*
-cpp/test/phonenumbers/geocoding/geocoding_test_data.cc
-java/build/
-java/demo/war/WEB-INF/classes/
-java/demo/war/WEB-INF/lib/
-java/**/target/
-# Ignore the logs directory
-/logs/
-# Ignore ourselves because this is not intended to be submitted.
-/.gitignore
+target/
+!tools/java/cpp-build/target/cpp-build-1.0-SNAPSHOT-jar-with-dependencies.jar
+build/
+lib/
+generated/