fix(tex): inline math should use \(...\) instead of $...$.

Also, I changed the snippet to `$$` which is easier to trigger and is
related to the snippet.

Author: cristobaltapia

UltiSnips/tex.snippets

@@ -309,8 +309,8 @@ snippet DD "D" w
 \mathbb{D}
 endsnippet
 
-snippet im "Inline Math" w
-$${1}$
+snippet $$ "Inline Math" iA
+\\(${1}\\) $0
 endsnippet
 
 snippet dm "Display Math" w