chore(deps): update ghcr.io/matrix-org/sliding-sync docker tag to v0.99.16

roles/custom/matrix-sliding-sync/defaults/main.yml

@@ -6,7 +6,7 @@
 matrix_sliding_sync_enabled: true
 
 # renovate: datasource=docker depName=ghcr.io/matrix-org/sliding-sync
-matrix_sliding_sync_version: v0.99.15
+matrix_sliding_sync_version: v0.99.16
 
 matrix_sliding_sync_scheme: https