CMakeLists.txt: rm libwebpmux dep from anim_{diff,dump}

Change-Id: Ic293affca5a3e17afbfcda5e96eb101d005621b8
diff --git a/CMakeLists.txt b/CMakeLists.txt
index efa93ed..128235c 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -636,7 +636,6 @@
                         imageenc
                         imageioutil
                         webp
-                        libwebpmux
                         webpdemux
                         ${WEBP_DEP_GIF_LIBRARIES})
   target_include_directories(anim_diff PRIVATE ${CMAKE_CURRENT_BINARY_DIR}/src)
@@ -652,7 +651,6 @@
                         imageenc
                         imageioutil
                         webp
-                        libwebpmux
                         webpdemux
                         ${WEBP_DEP_GIF_LIBRARIES})
   target_include_directories(anim_dump PRIVATE ${CMAKE_CURRENT_BINARY_DIR}/src)