Fix RSA Encryption Example

RSA Encryption Example is missing a closing comment bracket */

doc/crypt.tex

@@ -4591,7 +4591,7 @@ int main(void)
       return EXIT_FAILURE;
    }
 
-   /* register a math library (in this case TomsFastMath)
+   /* register a math library (in this case TomsFastMath) */
    ltc_mp = tfm_desc;
 
    if (register_hash(&sha1_desc) == -1) {