general UI: Add a description for the message edit icon.
general UI: Add a description for the message edit icon.

Fixes #7745.

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