Update tex.snippets

`b` trigger is renamed to `bf`

Author: ckunte

UltiSnips/tex.snippets

@@ -201,7 +201,7 @@ snippet em "emphasize" i
 \emph{$1}$0
 endsnippet
 
-snippet b "bold" i
+snippet bf "bold" i
 \textbf{$1}$0
 endsnippet