[unbload] drop meaningless field `number_of_results_xpath` from results (#6130)

In the result-list, the ``number_of_results`` indicate the number of hits in the
Index, they do not indicate how many results are in the answer.

In the past, search engines such as google or ddg had an indication on the first
page of a search term of how many hits there were for this term in total in
their index.

This info was added up in SearXNG and delivered under ``number_of_results``.
Nowadays the search engines no longer indicate how many hits there are in the
index and so this field in SearXNG is also superfluous.

- https://github.com/searxng/searxng/issues/2457#issuecomment-2566181574
- https://github.com/searxng/searxng/issues/2987
- https://github.com/searxng/searxng/issues/5034

Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>

searx/results.py

@@ -69,7 +69,6 @@ class ResultContainer:
         self.answers = AnswerSet()
         self.corrections = set()
 
-        self._number_of_results: list[int] = []
         self.engine_data: dict[str, dict[str, str]] = defaultdict(dict)
         self._closed: bool = False
         self.paging: bool = False
@@ -135,11 +134,6 @@ class ResultContainer:
                         self._merge_infobox(result)
                     continue
 
-                if "number_of_results" in result:
-                    if self.on_result(result):
-                        self._number_of_results.append(result["number_of_results"])
-                    continue
-
                 if "engine_data" in result:
                     if self.on_result(result):
                         if result.engine:
@@ -252,25 +246,6 @@ class ResultContainer:
         self._main_results_sorted = gresults
         return self._main_results_sorted
 
-    @property
-    def number_of_results(self) -> int:
-        """Returns the average of results number, returns zero if the average
-        result number is smaller than the actual result count."""
-
-        if not self._closed:
-            log.error("call to ResultContainer.number_of_results before ResultContainer.close")
-            return 0
-
-        with self._lock:
-            resultnum_sum = sum(self._number_of_results)
-            if not resultnum_sum or not self._number_of_results:
-                return 0
-
-            average = int(resultnum_sum / len(self._number_of_results))
-            if average < len(self.get_ordered_results()):
-                average = 0
-            return average
-
     def add_unresponsive_engine(self, engine_name: str, error_type: str, suspended: bool = False):
         with self._lock:
             if self._closed: