resolver: Fix for moved package.

resolver/Dockerfile

 FROM alpine:3.21
 # hadolint ignore=DL3018
-RUN echo '@testing http://dl-cdn.alpinelinux.org/alpine/edge/testing' >> /etc/apk/repositories && \
+RUN echo '@community http://dl-cdn.alpinelinux.org/alpine/edge/community' >> /etc/apk/repositories && \
     apk add --update --no-cache \
         bash \
         dma \
-        gosu@testing \
+        gosu@community \
         iproute2 \
         knot-resolver \
         knot-utils \