Remove { and } from VALID_INPUT_CHARS in latex.txt

Resolves: moebiuscurve#27

{ and } were used long ago in the original version of latex.txt, but they are not used anymore since

    commit 879b138
    Author: Giuseppe Castagna <[email protected]>
    Date:   Wed Jul 23 08:41:30 2014 +0200

        Updates and bugfixes for the LaTeX table by Giuseppe Castagna (original author of the LaTeX table)

Therefore, they should not be in VALID_INPUT_CHARS.

tables/latex.txt

@@ -55,7 +55,7 @@ DEF_FULL_WIDTH_LETTER = FALSE
 MAX_KEY_LENGTH = 20
 
 ### Valid input chars.
-VALID_INPUT_CHARS = abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890^\_[]{}
+VALID_INPUT_CHARS = abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890^\_[]
 
 ### Start characters, every key in the table starts with one of these characters
 START_CHARS = \_^