unprivileged/integrated-matrix: Drop the Specialized Extensions section (Zvvhpc, Zvvaimlfp, Zvvaimlint)

[ptomsich]

Remove the three specialised bundles (Zvvhpc, Zvvaimlfp, Zvvaimlint) from the spec. These were defined solely as named groupings of the existing computational extensions for HPC, AI/ML floating-point, and AI/ML integer workloads respectively, and added no new instructions or arithmetic semantics.

Bundle composition is properly the concern of profiles, not of an unprivileged ISA extension specification:

• Profiles can mandate concrete sets of extensions per application domain with finer granularity than three coarse bundles (and can reflect the fact that real platforms typically span multiple domains).
• The three bundles overlapped (the closing NOTE explicitly stated they are not mutually exclusive), so they did not partition the implementation space and were not load-bearing for interoperability.
• Open questions raised in TG review -- whether Zvvhpc should forbid psm=1, whether Zvvaimlfp should require narrow accumulators, whether AI/ML int and FP belong in one combined bundle -- are profile-level decisions that the spec should not pre-empt.

The 98-line section is removed in its entirety. No cross-references elsewhere in the spec point into it; no other prose change is required.