Replace code.google references with matching gitHub or cloud.google ones.
Three is one place that I didn't change as it does not have a corresponding one (I think
we missed it when copying the documentation - markgoldstein@ ?)
It is: https://cs.corp.google.com/#piper///depot/google3/third_party/java_src/appengine_mapreduce2/java/com/google/appengine/tools/mapreduce/inputs/DatastoreShardStrategy.java&l=237

R=tkaitchuck,markgoldstein
DELTA=20 (0 added, 0 deleted, 20 changed)

Revision created by MOE tool push_codebase.
MOE_MIGRATION=7166