Remove the excessive ccache in the command

MaChengxin · web-flow · commit 6af5af7ab18a · 2017-02-15T22:40:15.000+01:00
It is the same as the one at the end of the command.
diff --git a/doc/source/quickstart.rst b/doc/source/quickstart.rst
@@ -67,7 +67,7 @@ install most of these with::
 
     sudo dpkg --add-architecture i386
     sudo apt-get update
-    sudo apt-get install -y build-essential ccache git zlib1g-dev python2.7 python2.7-dev libncurses5:i386 libstdc++6:i386 zlib1g:i386 openjdk-7-jdk unzip ant ccache
+    sudo apt-get install -y build-essential git zlib1g-dev python2.7 python2.7-dev libncurses5:i386 libstdc++6:i386 zlib1g:i386 openjdk-7-jdk unzip ant ccache
 
 On Arch Linux (64 bit) you should be able to run the following to
 install most of the dependencies (note: this list may not be
