Update pyyaml from 6.0.2 to 6.0.3 (#1045)

Author: pyup-bot

requirements/requirements_synapse.txt

@@ -9,7 +9,7 @@ msgpack==1.1.0
 xxhash==3.5.0
 lmdb==1.7.3
 regex==2025.7.34
-PyYAML==6.0.2
+PyYAML==6.0.3
 prompt-toolkit==3.0.51
 Pygments==2.19.2
 lark==1.2.2