Revert "Truncate tar command output"

This reverts commit 1ec50e4.

It is not entirely clear to me how, but the recent archives appear
truncated after adding the `head` command with the previous commit,
resulting in travis-ci/travis-ci#8764.

This revert should resolve the issue.

Author: BanzaiMan

bin/archive

@@ -38,7 +38,7 @@ fi
 
 for DEST in $DESTS ; do
   mkdir -p $(dirname $DEST)
-  tar -cjvf $DEST $TAR_PATHS | head -c 10000
+  tar -cjvf $DEST $TAR_PATHS
 
   pushd $(dirname $DEST) &>/dev/null