fix: hold GIL when working with py_obj

Author: RaphDal

src/questdb/dataframe.pxi

@@ -149,7 +149,7 @@ cdef enum col_source_t:
     col_source_dt64ns_numpy =           501000
     col_source_dt64ns_tz_arrow =        502000
     col_source_arr_f64_numpyobj =       601100
-    col_source_decimal_pyobj =          701000
+    col_source_decimal_pyobj =          701100
     col_source_decimal32_arrow =        702100
     col_source_decimal64_arrow =        703100
     col_source_decimal128_arrow =       704100