Remove broken function replace_kw from ResdataFile

This function referenced the field data_owner from
ResdataKw which is never set, except after the lookup
and then it is set to False.

The only possible outcome of calling the function is
AttributeError so we are only removing undefined behavior
in terms of semver.

python/resdata/resfile/rd_file.py

@@ -51,9 +51,6 @@ class ResdataFile(BaseCClass):
         "int rd_file_get_restart_index(rd_file, rd_time_t)"
     )
     _get_src_file = ResdataPrototype("char* rd_file_get_src_file(rd_file)")
-    _replace_kw = ResdataPrototype(
-        "void rd_file_replace_kw(rd_file, rd_kw, rd_kw, bool)"
-    )
     _fwrite = ResdataPrototype("void rd_file_fwrite_fortio(rd_file, rd_fortio, int)")
     _has_report_step = ResdataPrototype("bool rd_file_has_report_step(rd_file, int)")
     _has_sim_time = ResdataPrototype("bool rd_file_has_sim_time(rd_file, rd_time_t)")
@@ -435,40 +432,6 @@ def restart_get_kw(self, kw_name, dtime, copy=False):
                 'Does not have keyword "%s" at time:%s.' % (kw_name, dtime)
             )
 
-    def replace_kw(self, old_kw, new_kw):
-        """
-        Will replace @old_kw with @new_kw in current ResdataFile instance.
-
-        This method can be used to replace one of the ResdataKW instances
-        in the current ResdataFile. The @old_kw reference must be to the
-        actual ResdataKW instance in the current ResdataFile instance (the
-        final comparison is based on C pointer equality!), i.e. it
-        must be a reference (not a copy) from one of the ??get_kw??
-        methods of the ResdataFile class. In the example below we replace
-        the SWAT keyword from a restart file:
-
-           swat = file.iget_named_kw( "SWAT" , 0 )
-           new_swat = swat * 0.25
-           file.replace_kw( swat , new_swat )
-
-
-        The C-level rd_file_type structure takes full ownership of
-        all installed rd_kw instances; mixing the garbage collector
-        into it means that this is quite low level - and potentially
-        dangerous!
-        """
-
-        # We ensure that this scope owns the new_kw instance; the
-        # new_kw will be handed over to the rd_file instance, and we
-        # can not give away something we do not alreeady own.
-        if not new_kw.data_owner:
-            new_kw = ResdataKW.copy(new_kw)
-
-        # The rd_file instance will take responsability for freeing
-        # this rd_kw instance.
-        new_kw.data_owner = False
-        self._replace_kw(old_kw, new_kw, False)
-
     @property
     def size(self):
         """