Fix a small typo in the docs (GH-26991) (GH-27003)

(cherry picked from commit a79e2b6)

Co-authored-by: Srinivas Reddy Thatiparthy (శ్రీనివాస్  రెడ్డి తాటిపర్తి) <[email protected]>

Co-authored-by: Srinivas Reddy Thatiparthy (శ్రీనివాస్  రెడ్డి తాటిపర్తి) <[email protected]>

Author: miss-islington

Doc/c-api/memory.rst

@@ -488,7 +488,7 @@ Customize Memory Allocators
 Debug hooks on the Python memory allocators
 ===========================================
 
-When :ref:`Python is built is debug mode <debug-build>`, the
+When :ref:`Python is built in debug mode <debug-build>`, the
 :c:func:`PyMem_SetupDebugHooks` function is called at the :ref:`Python
 preinitialization <c-preinit>` to setup debug hooks on Python memory allocators
 to detect memory errors.