MDEV-23190 after-merge fix: remove unused code

The merge commit 4d4865de
introduced fil_space_t::max_page_number_of_io() with no callers.

storage/innobase/include/fil0fil.h

@@ -415,15 +415,6 @@ struct fil_space_t
 
 	ulint		magic_n;/*!< FIL_SPACE_MAGIC_N */
 
-  /** Clamp a page number for batched I/O, such as read-ahead.
-  @param offset   page number limit
-  @return offset clamped to the tablespace size */
-  ulint max_page_number_for_io(ulint offset) const
-  {
-    const ulint limit= committed_size;
-    return limit > offset ? offset : limit;
-  }
-
 	/** @return whether doublewrite buffering is needed */
 	bool use_doublewrite() const
 	{