[3.15] Fix typo in C API Type Object Structures documentation (GH-154249) (#154250)

(cherry picked from commit 86e1fed)

Co-authored-by: Michael Newman <michael.b.newman@gmail.com>

Author: miss-islington

Doc/c-api/typeobj.rst

@@ -3051,7 +3051,7 @@ Buffer Object Structures
 
    * Resource cleanup when the counter reaches zero must be done atomically,
      as the final release may race with concurrent releases from other
-     threads and dellocation must only happen once.
+     threads and deallocation must only happen once.
 
    The exporter MUST use the :c:member:`~Py_buffer.internal` field to keep
    track of buffer-specific resources. This field is guaranteed to remain