dashboard: rename freebsd-arm to freebsd-arm-paulzhol

I didn't realize that the freebsd-arm builder was actually called
freebsd-arm-paulzhol before and I mistakenly created the replacement
buildet-based builder as "freebsd-arm".

Name it how it was.

Change-Id: Ib7d73947ce599c82c628ab323001213e1b4ee20b
Reviewed-on: https://go-review.googlesource.com/53358
Reviewed-by: Brad Fitzpatrick <[email protected]>

Author: bradfitz

dashboard/builders.go

@@ -1216,7 +1216,7 @@ func init() {
 		SkipSnapshot: true,
 	})
 	addBuilder(BuildConfig{
-		Name:         "freebsd-arm",
+		Name:         "freebsd-arm-paulzhol",
 		HostType:     "host-freebsd-arm-paulzhol",
 		SkipSnapshot: true,
 		env: []string{