pages: Fix deploy key check on GHE
pages: Fix deploy key check on GHE

Remove a hardcoded github.com in the pages provider's deploy key
validation check, which breaks deployment pipelines running against
GitHub Enterprise.

Signed-off-by: afzhou <54dd16f8bac4793e88c20bcab359f8d4ede62663@ibm.com>

travis-ci/dpl,travis-ci/dpl,travis-ci/dpl