Fix minor typos in unicode.rst (GH-149587)

(cherry picked from commit 4e97ff3)

Co-authored-by: Manoj K M <manojkmdev24@gmail.com>

Author: manoj-km24

Doc/c-api/unicode.rst

@@ -749,7 +749,7 @@ APIs:
    The string must not have been “used” yet.
    See :c:func:`PyUnicode_New` for details.
 
-   Return the number of written character, or return ``-1`` and raise an
+   Return the number of written characters, or return ``-1`` and raise an
    exception on error.
 
    .. versionadded:: 3.3
@@ -1161,7 +1161,7 @@ These are the UTF-8 codec APIs:
    .. versionadded:: 3.3
 
    .. versionchanged:: 3.7
-      The return type is now ``const char *`` rather of ``char *``.
+      The return type is now ``const char *`` rather than ``char *``.
 
    .. versionchanged:: 3.10
       This function is a part of the :ref:`limited API <limited-c-api>`.
@@ -1183,7 +1183,7 @@ These are the UTF-8 codec APIs:
    .. versionadded:: 3.3
 
    .. versionchanged:: 3.7
-      The return type is now ``const char *`` rather of ``char *``.
+      The return type is now ``const char *`` rather than ``char *``.
 
 
 UTF-32 Codecs