Update matrixdotorg/mjolnir Docker tag to v1.8.1

roles/custom/matrix-bot-mjolnir/defaults/main.yml

@@ -5,7 +5,7 @@
 matrix_bot_mjolnir_enabled: true
 
 # renovate: datasource=docker depName=matrixdotorg/mjolnir
-matrix_bot_mjolnir_version: "v1.8.0"
+matrix_bot_mjolnir_version: "v1.8.1"
 
 matrix_bot_mjolnir_container_image_self_build: false
 matrix_bot_mjolnir_container_image_self_build_repo: "https://github.com/matrix-org/mjolnir.git"