docs: Update redmine integration documentation.
docs: Update redmine integration documentation.

With some textual tweaks by tabbott.

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