Revert "Merge pull request #146 from ngiger/verify_downloads"

This reverts commit 4494a71285f030d18f258c6b245019eccd8146e5, reversing
changes made to 9395d3fdd74cd43f03b1844fbb0c3e48d713cbc1.
diff --git a/Dockerfile b/Dockerfile
index 64d1fe3..2d687f0 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,6 +1,6 @@
 FROM java:8-jdk
 
-RUN apt-get update && apt-get install -y wget git curl zip file && rm -rf /var/lib/apt/lists/*
+RUN apt-get update && apt-get install -y wget git curl zip && rm -rf /var/lib/apt/lists/*
 
 ENV JENKINS_HOME /var/jenkins_home
 ENV JENKINS_SLAVE_AGENT_PORT 50000