python: Fix missing argument from build_query_tree

[fabianfreyer]

In 545bf4f (#23), a fourth argument to builder::build_query_tree was introduced, but not added to the python bindings.

Building with cargo build --features "python" fails with:

error[E0061]: this function takes 4 arguments but 3 arguments were supplied
  --> src/python.rs:38:14
   |
38 |     let qt = crate::builder::build_query_tree(q, &mut c, false);
   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ -  ------  ----- supplied 3 arguments
   |              |
   |              expected 4 arguments
   |
note: function defined here
  --> src/builder.rs:28:8
   |
28 | pub fn build_query_tree(
   |        ^^^^^^^^^^^^^^^^
29 |     source: &str,
   |     ------------
30 |     cursor: &mut TreeCursor,
   |     -----------------------
31 |     is_cpp: bool,
   |     ------------
32 |     regex_constraints: Option<RegexMap>,
   |     -----------------------------------

For more information about this error, try `rustc --explain E0061`.
error: could not compile `weggli` due to previous error

This fixes the python build.

[felixwilhelm]

Thanks! I should really add tests for the Python API