update shebangs language configuration for Tcl

[achou11]

The primary executable that comes with Tcl is tclsh. Not really sure what tclish is, as I initially thought it was a typo. However, there seems to be references to it based on a quick search (e.g. here and here), so maybe it's a valid executable that I just haven't been aware of. I was hesitant to replace it and instead opted to just add tclsh.