Remove unused form auto-submit hook

[linkdata]

Summary

• Remove the undocumented data-jawsonchangesubmit browser hook.
• Keep the Number test focused on its change event and exact Input frame; Range still uses input.

Rationale

Public GitHub code search found the attribute only in JaWS's listener and test. A search of fresh default-branch clones of the six public linkdata repositories found through their JaWS go.mod dependency (edm-loadgen, jawsauth, jawsdemo, jawstree, rinse, and xyzzy) found no use. Private downstream use cannot be determined from this search.

The hook has no Go emitter or documentation. It also calls form.submit(), which skips validation and submit handlers, and throws when the marked element has no owning form. Removing it takes the unused-hook option described in the issue. Number's data-jawsnumber change routing remains intact.

Checks

• git diff --check passed.
• Repository search found no remaining jawsonchangesubmit references.
• Tests were not run.

Closes #506