e2e: remove docker engine testing remnants

These changes were made as part of the `docker engine` feature
in commit fd2f1b3b66, but later
reverted in f250152bf4 and
b7ec4a42d9

These lines were forgotten to be removed, and should no longer
be needed.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

dockerfiles/Dockerfile.e2e

@@ -1,7 +1,5 @@
 ARG GO_VERSION=1.12.6
 
-FROM docker/containerd-shim-process:a4d1531 AS containerd-shim-process
-
 # Use Debian based image as docker-compose requires glibc.
 FROM golang:${GO_VERSION}
 
@@ -9,10 +7,6 @@ RUN apt-get update && apt-get install -y \
     build-essential \
     curl \
     openssl \
-    btrfs-tools \
-    libapparmor-dev \
-    libseccomp-dev \
-    iptables \
     openssh-client \
     && rm -rf /var/lib/apt/lists/*