Fix Python execution with autocrlf on Windows

If the interp file contains CRLF, the \r is read as part of the
executable file name, and gimp searches for python3.exe\r.

(cherry picked from commit b134da1f39)

app/plug-in/gimpinterpreterdb.c

@@ -291,6 +291,7 @@ gimp_interpreter_db_add_program (GimpInterpreterDB  *db,
 
   name = buffer;
   program = p + 1;
+  g_strchomp (program);
 
   if (! g_file_test (program, G_FILE_TEST_IS_EXECUTABLE))
     {