py-h5py: Use float16 datatype only if available

[ryandesign]

Description

Closes: https://trac.macports.org/ticket/69938

Also remove reinplace that hasn't been needed since 3.6.0.

Type(s)

• bugfix
• enhancement
• security fix

Tested on

macOS 12.7.4 21H1123 x86_64
Xcode 14.2 14C18

Verification

Have you

• followed our Commit Message Guidelines?
• squashed and minimized your commits?
• checked that there aren't other open pull requests for the same change?
• referenced existing tickets on Trac with full URL in commit message?
• checked your Portfile with port lint --nitpick?
• tried existing tests with sudo port test?
• tried a full install with sudo port -vst install?
• tested basic functionality of all binary files?
• checked that the Portfile's most important variants haven't been broken?

[macportsbot]

Notifying maintainers:
@eborisch for port py-h5py.