Updated libgit2 example

[UebelAndre]

This will hopefully fix the following errors

(19:20:12) WARNING: Download from https://github.com/libgit2/libgit2/releases/download/v1.1.0/libgit2-1.1.0.tar.gz failed: class com.google.devtools.build.lib.bazel.repository.downloader.UnrecoverableHttpException GET returned 400 The request URI is invalid.
(19:20:12) ERROR: An error occurred during the fetch of repository 'libgit2':
   Traceback (most recent call last):
	File "/var/lib/buildkite-agent/.cache/bazel/_bazel_buildkite-agent/90e2e9b2d72fa9b00c19ff0535bb31ae/external/bazel_tools/tools/build_defs/repo/http.bzl", line 111, column 45, in _http_archive_impl
		download_info = ctx.download_and_extract(
Error in download_and_extract: java.io.IOException: Error downloading [https://github.com/libgit2/libgit2/releases/download/v1.1.0/libgit2-1.1.0.tar.gz] to /var/lib/buildkite-agent/.cache/bazel/_bazel_buildkite-agent/90e2e9b2d72fa9b00c19ff0535bb31ae/external/libgit2/temp4142249548117265753/libgit2-1.1.0.tar.gz: GET returned 400 The request URI is invalid.
(19:20:12) ERROR: Error fetching repository: Traceback (most recent call last):
	File "/var/lib/buildkite-agent/.cache/bazel/_bazel_buildkite-agent/90e2e9b2d72fa9b00c19ff0535bb31ae/external/bazel_tools/tools/build_defs/repo/http.bzl", line 111, column 45, in _http_archive_impl
		download_info = ctx.download_and_extract(
Error in download_and_extract: java.io.IOException: Error downloading [https://github.com/libgit2/libgit2/releases/download/v1.1.0/libgit2-1.1.0.tar.gz] to /var/lib/buildkite-agent/.cache/bazel/_bazel_buildkite-agent/90e2e9b2d72fa9b00c19ff0535bb31ae/external/libgit2/temp4142249548117265753/libgit2-1.1.0.tar.gz: GET returned 400 The request URI is invalid.