Fix note markup (#16805).

Patch by Tshepang Lekhonkhobe, reviewed by Georg Brandl.

Doc/c-api/arg.rst

@@ -45,6 +45,7 @@ in any early abort case).
 Unless otherwise stated, buffers are not NUL-terminated.
 
 .. note::
+
    For all ``#`` variants of formats (``s#``, ``y#``, etc.), the type of
    the length argument (int or :c:type:`Py_ssize_t`) is controlled by
    defining the macro :c:macro:`PY_SSIZE_T_CLEAN` before including

Doc/c-api/init.rst

@@ -548,6 +548,7 @@ code, or when embedding the Python interpreter:
    .. index:: module: _thread
 
    .. note::
+
       When only the main thread exists, no GIL operations are needed. This is a
       common situation (most Python programs do not use threads), and the lock
       operations slow the interpreter down a bit. Therefore, the lock is not