Use main by default

Change-Id: I361ce25fdd03f531eec6bdceb043f3c00d6acbba

CMakeLists.txt

diff --git a/CMakeLists.txt b/CMakeLists.txt
index e44cba0..154183b 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -47,6 +47,7 @@
   ExternalProject_Add(
     libavif
     GIT_REPOSITORY https://github.com/AOMediaCodec/libavif
+    GIT_TAG main
     PATCH_COMMAND cd ${CMAKE_BINARY_DIR}/libavif-prefix/src/libavif/ext &&
                   ./aom.cmd
     UPDATE_DISCONNECTED 1 # Avoid building aom everytime.