cmd/go/testdata/script: fix typo in get_domain_root.txt

golang.org/cl/214141 introduced the typo 'skup' for 'skip', which
broke tests. This change fixes it.

Change-Id: I1b3c230b545f1c093d3e0feedc3b41f3f0b41bec
Reviewed-on: https://go-review.googlesource.com/c/go/+/220157
Run-TryBot: Michael Matloob <matloob@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>

Author: matloob

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

@@ -2,7 +2,7 @@
 # go get foo.io (not foo.io/subdir) was not working consistently.
 
 [!net] skip
-[!exec:git] skup
+[!exec:git] skip
 
 # go-get-issue-9357.appspot.com is running
 # the code at github.com/rsc/go-get-issue-9357,