Changes for CF-1.10

[davidhassell]

CF-1.10 will be frozen on 7th August 2022. At the time of creating this issue, no changes to cfdm are required to be CF-1.10-compliant, other than setting __cf_version__ = 1.10.

Edit Assuming that nothing else cops up before then, CF-1.10 can be rolled out with v1.9.1.0, which is being released at the start of September 2022. The versioning strategy tells us that all CF-1.10 releases should start 1.10, so the new version of cfdm will in fact be 1.10.0.0.

[davidhassell]

The cut-off date for CF-1.10 has passed, with no further changes for required.