go.mod: update kevinburke/ssh_config to v1.2.0 (#19286)

Previously if you tried to read a HostName in a config file that
looked like this:

```
Host github
    HostName github.com        # This is the host for code review
```

DefaultUserSettings.Get("HostName") would return "github.com        ",
which I think is unintuitive and unexpected.

This behavior is fixed in v1.2 which would return "github.com" in the
above example.

go.mod

@@ -203,7 +203,7 @@ require (
 	github.com/jhump/protoreflect v1.8.2 // indirect
 	github.com/jonboulle/clockwork v0.2.2 // indirect
 	github.com/josharian/intern v1.0.0 // indirect
-	github.com/kevinburke/ssh_config v1.1.0 // indirect
+	github.com/kevinburke/ssh_config v1.2.0 // indirect
 	github.com/klauspost/pgzip v1.2.5 // indirect
 	github.com/kr/pretty v0.3.0 // indirect
 	github.com/kr/text v0.2.0 // indirect

go.sum

@@ -1004,8 +1004,8 @@ github.com/kballard/go-shellquote v0.0.0-20180428030007-95032a82bc51 h1:Z9n2FFNU
 github.com/kballard/go-shellquote v0.0.0-20180428030007-95032a82bc51/go.mod h1:CzGEWj7cYgsdH8dAjBGEr58BoE7ScuLd+fwFZ44+/x8=
 github.com/kevinburke/ssh_config v0.0.0-20190725054713-01f96b0aa0cd/go.mod h1:CT57kijsi8u/K/BOFA39wgDQJ9CxiF4nAY/ojJ6r6mM=
 github.com/kevinburke/ssh_config v0.0.0-20201106050909-4977a11b4351/go.mod h1:CT57kijsi8u/K/BOFA39wgDQJ9CxiF4nAY/ojJ6r6mM=
-github.com/kevinburke/ssh_config v1.1.0 h1:pH/t1WS9NzT8go394IqZeJTMHVm6Cr6ZJ6AQ+mdNo/o=
+github.com/kevinburke/ssh_config v1.2.0 h1:x584FjTGwHzMwvHx18PXxbBVzfnxogHaAReU4gf13a4=
-github.com/kevinburke/ssh_config v1.1.0/go.mod h1:CT57kijsi8u/K/BOFA39wgDQJ9CxiF4nAY/ojJ6r6mM=
+github.com/kevinburke/ssh_config v1.2.0/go.mod h1:CT57kijsi8u/K/BOFA39wgDQJ9CxiF4nAY/ojJ6r6mM=
 github.com/keybase/go-crypto v0.0.0-20200123153347-de78d2cb44f4 h1:cTxwSmnaqLoo+4tLukHoB9iqHOu3LmLhRmgUxZo6Vp4=
 github.com/keybase/go-crypto v0.0.0-20200123153347-de78d2cb44f4/go.mod h1:ghbZscTyKdM07+Fw3KSi0hcJm+AlEUWj8QLlPtijN/M=
 github.com/kisielk/errcheck v1.1.0/go.mod h1:EZBBE59ingxPouuu3KfxchcWSUPOHkagtvWXihfKN4Q=