tests: Use get_account_data_dict helper in some github tests.
tests: Use get_account_data_dict helper in some github tests.

The helper should be used instead of constructing the dict manually.

Change get_account_data_dict, on GitHubAuthBackendTest
class, so it has a third argument, user_avatar_url.

This is a preparation for support using GitHub avatar
upon user resgistration (when the user logs using
GitHub).

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