bpo-44964: Correct the note about the f_lasti field (GH-28208)

Doc/reference/datamodel.rst

@@ -1069,9 +1069,8 @@ Internal types
       :attr:`f_code` is the code object being executed in this frame; :attr:`f_locals`
       is the dictionary used to look up local variables; :attr:`f_globals` is used for
       global variables; :attr:`f_builtins` is used for built-in (intrinsic) names;
-      :attr:`f_lasti` gives the precise instruction (it represents a wordcode index, which
-      means that to get an index into the bytecode string of the code object it needs to be
-      multiplied by 2).
+      :attr:`f_lasti` gives the precise instruction (this is an index into the
+      bytecode string of the code object).
 
       Accessing ``f_code`` raises an :ref:`auditing event <auditing>`
       ``object.__getattr__`` with arguments ``obj`` and ``"f_code"``.

Doc/whatsnew/3.10.rst

@@ -1952,7 +1952,8 @@ Changes in the C API
     offset instead of a simple offset into the bytecode string. This means that this
     number needs to be multiplied by 2 to be used with APIs that expect a byte offset
     instead (like :c:func:`PyCode_Addr2Line` for example). Notice as well that the
-    ``f_lasti`` member of ``FrameObject`` objects is not considered stable.
+    ``f_lasti`` member of ``FrameObject`` objects is not considered stable: please
+    use :c:func:`PyFrame_GetLineNumber` instead.
 
 CPython bytecode changes
 ========================