dispatch tests: Stop stubbing message_store.
dispatch tests: Stop stubbing message_store.

I am trying to use somewhat more realistic data
for data classes in the dispatch tests.  (We still
want to mostly stub UI stuff.)

shubhamdhama/zulip,showell/zulip,hackerkid/zulip,eeshangarg/zulip,eeshangarg/zulip,shubhamdhama/zulip,andersk/zulip,hackerkid/zulip,timabbott/zulip,rishig/zulip,timabbott/zulip,rishig/zulip,kou/zulip,kou/zulip,zulip/zulip,brainwane/zulip,eeshangarg/zulip,synicalsyntax/zulip,punchagan/zulip,hackerkid/zulip,tommyip/zulip,brainwane/zulip,tommyip/zulip,synicalsyntax/zulip,shubhamdhama/zulip,showell/zulip,timabbott/zulip,rishig/zulip,timabbott/zulip,punchagan/zulip,punchagan/zulip,rht/zulip,rht/zulip,andersk/zulip,rishig/zulip,shubhamdhama/zulip,synicalsyntax/zulip,andersk/zulip,rishig/zulip,punchagan/zulip,andersk/zulip,hackerkid/zulip,rht/zulip,tommyip/zulip,rht/zulip,showell/zulip,zulip/zulip,hackerkid/zulip,rht/zulip,brainwane/zulip,synicalsyntax/zulip,andersk/zulip,zulip/zulip,brainwane/zulip,kou/zulip,showell/zulip,timabbott/zulip,tommyip/zulip,synicalsyntax/zulip,showell/zulip,kou/zulip,eeshangarg/zulip,zulip/zulip,eeshangarg/zulip,shubhamdhama/zulip,kou/zulip,zulip/zulip,hackerkid/zulip,brainwane/zulip,hackerkid/zulip,timabbott/zulip,kou/zulip,brainwane/zulip,punchagan/zulip,shubhamdhama/zulip,rht/zulip,tommyip/zulip,eeshangarg/zulip,rishig/zulip,andersk/zulip,brainwane/zulip,rishig/zulip,rht/zulip,punchagan/zulip,kou/zulip,showell/zulip,tommyip/zulip,synicalsyntax/zulip,showell/zulip,zulip/zulip,andersk/zulip,punchagan/zulip,synicalsyntax/zulip,zulip/zulip,eeshangarg/zulip,tommyip/zulip,shubhamdhama/zulip,timabbott/zulip