Purge references to --netscape and --libpods, no longer in Pod::Html

Purge references to --netscape and --libpods, no longer in Pod::Html

The long deprecated --netscape flag was removed in commit 27b29ec338b08496.
This was originally added to control use of Netscape specific HTML
extensions, , but became a no-op when that functionality was removed.
--libpods was removed in commit 3b49d8d9ac841d8e.

However neither commit removed use of these flags by callers to Pod::Html,
notably in installhtml and the Makefiles that invoke it. Hence this commit.