Docker: Remove unnecessary workaround for BusyBox's "free" (#4199) (#4213)

systeminformation gets incorrect memory information due to BusyBox's
"free" issue.(#3409)
A workaround for avoiding it was made.

But it never works because the runner container has no effect.
It should be deleted.

Dockerfile

@@ -8,7 +8,6 @@ WORKDIR /misskey
 
 FROM base AS builder
 
-RUN unlink /usr/bin/free
 RUN apk add --no-cache \
     autoconf \
     automake \
@@ -20,7 +19,6 @@ RUN apk add --no-cache \
     make \
     nasm \
     pkgconfig \
-    procps \
     python \
     zlib-dev
 RUN npm i -g yarn