fix Dockerfile

Signed-off-by: kamiKAC <m.k.rudzki@gmail.com>

Author: kamiKAC

Dockerfile

@@ -15,11 +15,9 @@
 FROM quay.io/terraform-docs/terraform-docs:0.16.0
 
 # this is explicitly needed because yq v4.x only exists in this repo.
-RUN echo "http://dl-4.alpinelinux.org/alpine/edge/community" >> /etc/apk/repositories
-
-RUN set -x \
-    && apk update \
-    && apk add --no-cache \
+RUN apk add -X https://dl-4.alpinelinux.org/alpine/edge/community -u alpine-keys && \
+    apk update && \
+    apk add --no-cache \
         bash \
         git \
         git-lfs \