Add missing image file, correct typos

Add the missing TextInput_MultipleAnswer.gif file. Correct
capitalization of another image file name so it'll appear in the docs.

docs/course_authors/source/create_lti.rst

@@ -73,7 +73,7 @@ Step 1. Add LTI to the Advanced Modules Policy Key
    then enter **“lti”**. Make sure to include the quotation marks, but
    not the period.
    
-   .. image:: Images/LTI_Policy_Key.gif
+   .. image:: Images/LTI_policy_key.gif
 
    **Note** If the **Policy Value** field already contains text, place your
    cursor directly after the closing quotation mark for the final item, and

docs/course_authors/source/create_video.rst

@@ -182,7 +182,3 @@ Advanced Options
      - Additional locations where you've posted the video. This field must contain a URL that ends in .mpeg, .mp4, or .ogg.
    * - **YouTube ID, YouTube ID for .75x speed, YouTube ID for 1.25x speed, YouTube ID for 1.5x speed**
      - If you have uploaded separate videos to YouTube for different speeds of your video, enter the YouTube IDs for these videos in these fields.
-
-
-
-ƒf
\ No newline at end of file