Upgrade rules_pkg

The old rules result in this weird error that I can't figure out when
deploying the Julia runtime:

    $ sudo dpkg -i /tmp/frc971-scouting-julia_1_amd64.deb
    (Reading database ... 124346 files and directories currently installed.)
    Preparing to unpack .../frc971-scouting-julia_1_amd64.deb ...
    Unpacking frc971-scouting-julia (1) ...
    dpkg: error processing archive /tmp/frc971-scouting-julia_1_amd64.deb (--install):
     corrupted filesystem tarfile in package archive: unsupported PAX tar header type 'x'
    dpkg-deb: error: paste subprocess was killed by signal (Broken pipe)
    Errors were encountered while processing:
     /tmp/frc971-scouting-julia_1_amd64.deb

The new rules don't have this problem.

I also took this opportunity to drop a patch that we didn't need
anymore.

Signed-off-by: Philipp Schrader <philipp.schrader@gmail.com>
Change-Id: Iec2c0dcf27f76f83ab337da97a6caf0e182e706b
diff --git a/WORKSPACE b/WORKSPACE
index dd184d5..8a6206d 100644
--- a/WORKSPACE
+++ b/WORKSPACE
@@ -99,14 +99,10 @@
 
 http_archive(
     name = "rules_pkg",
-    patch_args = ["-p1"],
-    patches = [
-        "//third_party:rules_pkg/0001-Fix-tree-artifacts.patch",
-    ],
-    sha256 = "62eeb544ff1ef41d786e329e1536c1d541bb9bcad27ae984d57f18f314018e66",
+    sha256 = "8c20f74bca25d2d442b327ae26768c02cf3c99e93fad0381f32be9aab1967675",
     urls = [
-        "https://mirror.bazel.build/github.com/bazelbuild/rules_pkg/releases/download/0.6.0/rules_pkg-0.6.0.tar.gz",
-        "https://github.com/bazelbuild/rules_pkg/releases/download/0.6.0/rules_pkg-0.6.0.tar.gz",
+        "https://mirror.bazel.build/github.com/bazelbuild/rules_pkg/releases/download/0.8.1/rules_pkg-0.8.1.tar.gz",
+        "https://github.com/bazelbuild/rules_pkg/releases/download/0.8.1/rules_pkg-0.8.1.tar.gz",
     ],
 )