design: Make copy text button clickable again.
design: Make copy text button clickable again.

Due to added opacity of 0.5 through the readonly property, the button
for copy and close was not clickable. Increasing z-index of the button
solves it.

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