notification: Add a space in narrow to message content.
notification: Add a space in narrow to message content.

We have a space for this kind of texts in other places but somehow we
missed this case. This PR fixes the same.

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