subscriptions: Fix broken color property for .mute-note.
subscriptions: Fix broken color property for .mute-note.

Instead of changing the property to color, we use opacity for dark mode
compatibility.

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