Add new kokoro reader group.

In order to support Kokoro's migration to Pod, GoB reader permissions will now be granted through the ACL group kokoro-gob-readers(-qa) instead of directly to borg roles kokoro/kokoro-dedicated(-qa).

See go/kokoro-gob-permissions-update and b/266422763 for more details.

groups

diff --git a/groups b/groups
index 98209f4..cca152c 100644
--- a/groups
+++ b/groups
@@ -9,3 +9,4 @@
 mdb:gem5-gadmins                                              	mdb/gem5-gadmins
 mdb:kokoro                                                    	mdb/kokoro
 mdb:kokoro-dedicated                                          	mdb/kokoro-dedicated
+mdb:kokoro-gob-readers                                        	mdb/kokoro-gob-readers

project.config

diff --git a/project.config b/project.config
index 43f6a54..5a85f77 100644
--- a/project.config
+++ b/project.config
@@ -12,6 +12,7 @@
 	read = group mdb/gem5-gadmins
 	read = group mdb/kokoro
 	read = group mdb/kokoro-dedicated
+	read = group mdb/kokoro-gob-readers
 	revert = group Registered Users
 [access "refs/for/*"]
 	addPatchSet = group Registered Users