Correct “an” → “a” with “Unicode”, “user”, “UTF”, etc

This affects documentation and code comments.
diff --git a/Doc/c-api/unicode.rst b/Doc/c-api/unicode.rst
index 13a2807..3262354 100644
--- a/Doc/c-api/unicode.rst
+++ b/Doc/c-api/unicode.rst
@@ -234,7 +234,7 @@
 
 .. c:function:: PyObject *PyUnicode_FromString(const char *u)
 
-   Create a Unicode object from an UTF-8 encoded null-terminated char buffer
+   Create a Unicode object from a UTF-8 encoded null-terminated char buffer
    *u*.
 
    .. versionadded:: 2.6
@@ -347,7 +347,7 @@
 
 .. c:function:: PyObject* PyUnicode_FromEncodedObject(PyObject *obj, const char *encoding, const char *errors)
 
-   Coerce an encoded object *obj* to an Unicode object and return a reference with
+   Coerce an encoded object *obj* to a Unicode object and return a reference with
    incremented refcount.
 
    String and other char buffer compatible objects are decoded according to the
@@ -663,7 +663,7 @@
 
    If *Py_UNICODE_WIDE* is defined, a single :c:type:`Py_UNICODE` value may get
    represented as a surrogate pair. If it is not defined, each :c:type:`Py_UNICODE`
-   values is interpreted as an UCS-2 character.
+   values is interpreted as a UCS-2 character.
 
    Return *NULL* if an exception was raised by the codec.