fix new Dict show method on 1-character keys

I might be missing something, but that line of code doesn't seem to do
anything except replace 1-character strings with …
made "character" plural and tweaked commas
Merge pull request #7092 from catawbasam/patch-1

made "character" plural and tweaked commas
Define sqrt and cbrt as Unicode characters for pdflatex. Fix #7091
Parametrize Triangular on matrix type