Fix grammar issues (hand-picked from draft-2)

api.rst

@@ -1472,7 +1472,7 @@ Image data is collected by repeatedly calling
 :func:`sane_read()`. Eventually, this function will return
 an end-of-file status (:macro:`SANE_STATUS_EOF`). This
 indicates the end of the current frame. If the frontend expects
-additional frames (e.g., the individual channels in of a red/green/blue
+additional frames (e.g., the individual channels of a red/green/blue
 image or multiple images), it can call :func:`sane_start()`
 again. Once all desired frames have been acquired, function
 :func:`sane_cancel()` must be called. This operation can
@@ -1491,7 +1491,7 @@ resources (e.g., temporary files or locks) may remain unclaimed.
 Well-Known Options
 ------------------
 
-While most backend options are completely self-describing, there are a
+While most backend options are completely self-describing, there are
 cases where a user interface might want to special-case the handling of
 certain options. For example, the scan area is typically defined by four
 options that specify the top-left and bottom-right corners of the area.