bug#30548: conflicts with smartparens

[Alex Branham]

There are two smartparens bugs that may be related to this.

https://github.com/Fuco1/smartparens/issues/827

TLDR; enable delete-selection-mode *before* enabling smartparens

and also

https://github.com/Fuco1/smartparens/issues/834

And the workaround here is to rely on smartparens rather than auctex's 
implementation of $:

(define-key TeX-mode-map (kbd "$") #'self-insert-command)

Hope that helps,
Alex