streams: Update description for stream-privacy-type.
streams: Update description for stream-privacy-type.

Fixes #10524

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