Cave carver's "start_vertical_radius_multiplier" field is misspelled

As noted by the changelog for 26.3, the carver type “cave” has an optional field that multiplies the start of every tunnel segments vertical radius, listed as “start_vertical_radius_multiplier” in the changelog.

However, the field that the current release actually looks for is “start_vertical_radiues_multiplier” (an extra “e” letter where there shouldn’t be). This is likely a misspelling, but is one that made it to the full release.