[TLS] -draft8447bis: rename Support Group Elliptic curve groups space

[Sean Turner <[e-mail]>]

<author hat>

**WARNING: Potential bikeshed**

-connolly-tls-mlkem-key-agreement has suggested that code points for the NIST PQ be registered in the TLS Supported Groups IANA registry [1].  Currently [2], the registry is carved up into three blocks as follows:

Range: 0-255, 512-65535
Registration Procedures: Specification Required
Note: Elliptic curve groups

Range 256-511
Registration Procedures: Specification Required
Note: Finite Field Diffie-Hellman groups

Assuming that the proposal in -connolly-tls-mlkem-key-agreement is the path for PQ KEM algorithms (and maybe regardless of whether this is the path), we should really replace the “Elliptic curve groups” note in the 0-255, 512-65535 range row with something else.  I am open to suggestions, but would like to propose “unallocated”. I have submitted the following issue:
https://github.com/tlswg/rfc8447bis/issues/54
and this PR:
https://github.com/tlswg/rfc8447bis/pull/55
to address this.

spt

[1] https://www.iana.org/assignments/tls-parameters/tls-parameters.xhtml#tls-parameters-8

[2] Originally, RFC 8442 defined the name of the registry as "EC Named Curve Registry” and then RFC 7919 re-named it “Supported Groups” and carved out the FFDH space.