contrib: update dav1d to 1.4.3

1.4.3 is a very small release focused on security issues:
 - AArch64: Fix potential out of bounds access in DotProd H/HV filters
 - cli: Prevent buffer over-read

contrib/src/dav1d/SHA512SUMS

@@ -1 +1 @@
-36f8e632f64212db63e126b9ed2ca95c2db930d2388c551cde0b13b783ae872edeab1b5dd2274684bb03e98536d0334552ddcba209cff08c3568d97321034920  dav1d-1.4.2.tar.xz
+6f3233acfb7d248155ac4beb237fe48186fdfb378820f0b15a5ca54a5642a63ebae48446075f10c6be77a8b9a95ddf41c6709af21936af793f1bbc28a2ef4bd8  dav1d-1.4.3.tar.xz

contrib/src/dav1d/rules.mak

@@ -1,6 +1,6 @@
 # libdav1d
 
-DAV1D_VERSION := 1.4.2
+DAV1D_VERSION := 1.4.3
 DAV1D_URL := $(VIDEOLAN)/dav1d/$(DAV1D_VERSION)/dav1d-$(DAV1D_VERSION).tar.xz
 
 PKGS += dav1d