Revert "Document which registers are used for the async context on x86-64/ARM64. (#64947)"

This reverts commit 22150c5.

Author: grynspan

docs/ABI/CallConvSummary.rst

@@ -50,8 +50,7 @@ Register usage
 +-----------+----------------------------------+----------+----------+----------+
 | ``r13``   | Callee-saved register            |          |          | ``self`` |
 +-----------+----------------------------------+----------+----------+----------+
-| ``r14``   | Callee-saved register            |          |          | Async    |
-|           |                                  |          |          | context  |
+| ``r14``   | Callee-saved register            |          |          |          |
 +-----------+----------------------------------+----------+----------+----------+
 | ``r15``   | Callee-saved register            |          |          |          |
 |           | (other platforms use as GOT ptr) |          |          |          |
@@ -153,10 +152,7 @@ Register usage
 | ``x21``  |         | Callee-saved register   |          |          | Error    |
 |          |         |                         |          |          | return   |
 +----------+---------+-------------------------+----------+----------+----------+
-| ``x22``  |         | Callee-saved register   |          |          | Async    |
-|          |         |                         |          |          | context  |
-+----------+---------+-------------------------+----------+----------+----------+
-| ``x23``- |         | Callee-saved registers  |          |          |          |
+| ``x22``- |         | Callee-saved registers  |          |          |          |
 | ``x28``  |         |                         |          |          |          |
 +----------+---------+-------------------------+----------+----------+----------+
 | ``x29``  | ``fp``  | Frame pointer           |          |          |          |