man2html deploy: don't shallow-clone gh-pages

Need full history for git push to work.

.travis/man2html.sh

@@ -15,7 +15,7 @@ if ! git diff --name-only "$parent" "$head" | grep -Pq "doc/.*\.[1-8]$"; then
    exit 0
fi

git clone -b gh-pages --depth 3 "https://kernc:$GH_PASSWORD@github.com/$TRAVIS_REPO_SLUG.git" gh-pages
git clone -b gh-pages "https://kernc:$GH_PASSWORD@github.com/$TRAVIS_REPO_SLUG.git" gh-pages
groff -wall -mandoc -Thtml doc/xsuspender.1 > gh-pages/xsuspender.1.html
cd gh-pages
git commit -m "CI: Update xsuspender.1.html from $head" -- xsuspender.1.html