DOCS: Fix linkcheck for NCDC link
DOCS: Fix linkcheck for NCDC link

Sending "Accept-Encoding: gzip, deflate" as default for requests with a
HEAD request causes the server to disconnect. Override the headers for
this server to solve it.

Unidata/MetPy,Unidata/MetPy,dopplershift/MetPy,ShawnMurd/MetPy,dopplershift/MetPy