README.md: Change "AOM" (libaom) to "AV1"

(cherry picked from commit 99f4dbbf337c643654e74805d62795f6fb54e29d)

README.md

diff --git a/README.md b/README.md
index 83b90d6..081da00 100644
--- a/README.md
+++ b/README.md
@@ -5,7 +5,7 @@
 
 <https://aomediacodec.github.io/av1-avif/>
 
-It can encode and decode all AOM supported YUV formats and bit depths (with
+It can encode and decode all AV1 supported YUV formats and bit depths (with
 alpha).
 
 It is recommended that you check out/use