BaseRawIO: fix the has_buffer_description_api() check in get_analogsignal_buffer_description (#1930)

* BaseRawIO: the has_buffer_description_api() check tested the method object, not the result.

A reader with a false flag went directly to the private method. For a reader with a
method that shouldn't be used (like the Blackrock on PTP files) it returned a wrong
description with no errors. An ExampleRawIO reader, whos flag is False, must raise
ValueError.

* Remove the has_buffer_description_api test

---------

Co-authored-by: Colin McNabb <cmcnabb@blackrockneuro.com>

Author: cboulay

neo/rawio/baserawio.py

@@ -1544,7 +1544,7 @@ def _rescale_epoch_duration(self, raw_duration: np.ndarray, dtype: np.dtype):
     # buffer api zone
     # must be implemented if has_buffer_description_api=True
     def get_analogsignal_buffer_description(self, block_index: int = 0, seg_index: int = 0, buffer_id: str = None):
-        if not self.has_buffer_description_api:
+        if not self.has_buffer_description_api():
             raise ValueError("This reader do not support buffer_description API")
         descr = self._get_analogsignal_buffer_description(block_index, seg_index, buffer_id)
         return descr