Added 9c to list of tested libjpeg versions [ci skip]

Author: radarhere

docs/installation.rst

@@ -128,8 +128,8 @@ Many of Pillow's features require external libraries:
 
 * **libjpeg** provides JPEG functionality.
 
-  * Pillow has been tested with libjpeg versions **6b**, **8**, **9**, **9a**,
-    and **9b** and libjpeg-turbo version **8**.
+  * Pillow has been tested with libjpeg versions **6b**, **8**, **9-9c** and
+    libjpeg-turbo version **8**.
   * Starting with Pillow 3.0.0, libjpeg is required by default, but
     may be disabled with the ``--disable-jpeg`` flag.