cmd/go: skip the 'git' part of get_insecure_redirect in short mode

Invoking 'git' adds about 200ms to this test on a fast machine,
probably more on a slow one. (As a general habit we skip the
'git' tests uniformly in short mode.)

For #52545.

Change-Id: Iea6d86a8c9c8b0f1fe51888faf7f5fe7dd8f1eb3
Reviewed-on: https://go-review.googlesource.com/c/go/+/488236
Auto-Submit: Bryan Mills <[email protected]>
Reviewed-by: Than McIntosh <[email protected]>
Run-TryBot: Bryan Mills <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>

Author: Bryan C. Mills

src/cmd/go/testdata/script/get_insecure_redirect.txt

@@ -8,5 +8,7 @@ env GO111MODULE=off
 ! go get -d vcs-test.golang.org/insecure/go/insecure
 stderr 'redirected .* to insecure URL'
 
+[short] stop 'builds a git repo'
+
 env GOINSECURE=vcs-test.golang.org/insecure/go/insecure
 go get -d vcs-test.golang.org/insecure/go/insecure