Remove useless method declaration

"preprocessing" is not actually defined.

Author: tautschnig

jbmc/src/jdiff/jdiff_parse_options.h

@@ -67,8 +67,6 @@ class jdiff_parse_optionst : public parse_options_baset, public jdiff_languagest
     goto_modelt &goto_model);
 
   bool process_goto_program(const optionst &options, goto_modelt &goto_model);
-
-  void preprocessing();
 };
 
 #endif // CPROVER_JDIFF_JDIFF_PARSE_OPTIONS_H

src/goto-diff/goto_diff_parse_options.h

@@ -67,8 +67,6 @@ class goto_diff_parse_optionst:
     goto_modelt &goto_model);
 
   bool process_goto_program(const optionst &options, goto_modelt &goto_model);
-
-  void preprocessing();
 };
 
 #endif // CPROVER_GOTO_DIFF_GOTO_DIFF_PARSE_OPTIONS_H