Fix goTo* dialog bug with chat on Mac OSX

If chat was open, when pressing enter on Mac OSX the operation would not go through and
would focus on the chat window.  There seems to be a  deeper issue, but
it was decided to go with the simple solution of making these dialog
windows not of `Sheet` type.
Merge branch 'master' of git://github.com/highfidelity/hifi into 19828
Merge pull request #3130 from huffman/19828

Code Review for Job #19828