build: bump dep to fix dependency resolution bug

[benesch]

The version of dep we had vendored previously, v0.4.1, somehow dropped a
Windows-only dependency, github.com/shirou/w32, on the floor. Upgrade to
dep v0.5.0, which correctly brings in that dependency.

Release note: None

[cockroach-teamcity]

This change is 

[benesch]

diff --git a/Gopkg.lock b/Gopkg.lock
[15:29:15]	[Step 5/5] index e6cc07516..d9fed0426 100644
[15:29:15]	[Step 5/5] --- a/Gopkg.lock
[15:29:15]	[Step 5/5] +++ b/Gopkg.lock
[15:29:15]	[Step 5/5] @@ -2,6 +2,7 @@
[15:29:15]	[Step 5/5]  
[15:29:15]	[Step 5/5]  
[15:29:15]	[Step 5/5]  [[projects]]
[15:29:15]	[Step 5/5] +  digest = "1:257d8e2c9287f4f019bcf07b17160db066cebe2e1d4549a9d825e3083de36c8e"
[15:29:15]	[Step 5/5]    name = "cloud.google.com/go"
[15:29:15]	[Step 5/5]    packages = [
[15:29:15]	[Step 5/5]      "compute/metadata",
[15:29:15]	[Step 5/5] @@ -12,115 +13,151 @@
[15:29:15]	[Step 5/5]      "internal/version",
[15:29:15]	[Step 5/5]      "storage",
[15:29:15]	[Step 5/5]    ]
[15:29:15]	[Step 5/5] +  pruneopts = "UT"
[15:29:15]	[Step 5/5]    revision = "0fd7230b2a7505833d5f69b75cbd6c9582401479"
[15:29:15]	[Step 5/5]    version = "v0.23.0"
[15:29:15]	[Step 5/5]  

🤔

[benesch]

Well that was utterly baffling. I could only reproduce that diff by running github-pull-request-make on my GCE worker. But now that the pruneopts lines are everywhere, my macOS checkout is happy to preserve them. Gah!

[benesch]

Ok, I'm not going to think too hard about this because everything is happy now. Merging!

bors r=dt

[dt]

good call -- if you gaze too long into the abyss of a package manager, the abyss also gazes into you

[craig]

Build succeeded

• GitHub CI (Cockroach)