DDSXTY14 — Bad reference to RTPS leads to apparent circularity

The first sentence of page 215 says "As defined in the RTPS specification, a data encapsulation is identified by a two-byte value, the “encapsulation identifier” [RTPS].". But [RTPS] refers to DDSI-RTPS v2.3, which does not contain those terms. Those terms were last used in DDSI-RTPS v2.2. Instead, since v2.3 of DDSI-RTPS, we have a `SerializedPayload` instead of a "data encapsulation and a `RepresentationIdentifier` instead of an "encapsulation identifier". Furthermore, versions 2.3-2.5 (2.5 being the latest version at the time of this report) of DDSI-RTPS refer to DDS-XTypes v1.2 for the `RepresentationIdentifier`. DDS-XTypes v1.2 then refers to DDSI-RTPS v2.2. I haven't followed the chain further, but I think it should be broken in the next revision, with at least one of RTPS or XTypes ceasing to refer to the other.

In summary:

• DDS-XTypes v1.3 refers to something nonexistent in DDSI-RTPS v2.3.
• DDSI-RTPS v2.3+ refer to DDS-XTypes v1.2 on the same subject.
• DDS-XTypes v1.2 refers to DDSI-RTPS v2.2 on that subject.

Update 7.6.3.1.2 to align it with the new language in RTPS 2.5

Update 7.6.3.1.2 to use the terms in RTPS 2.5, including "RepresentationIdentifier" and RepresentationOptions. Remove obsolete text from the initial version of XTYPES which was referencing old versions of RTPS.