fix(form): compute isMin from min, not max

[173787247]

isMin is used to disable the delete button in the group and table extensions:

packages/form/src/extensions/group.vue:40   :class="{ disabled: disabled || isMin }" @click="del(index)"
packages/form/src/extensions/table.vue:89   :class="{ disabled: isMin }"

but it is computed from meta.max:

const isMax = computed(() => entries.value.length >= props.schema.meta.max)
const isMin = computed(() => entries.value.length >= props.schema.meta.max)

Two consequences:

• with both bounds set (Schema.array(X).min(2).max(5)) — at two entries isMin is
  2 >= 5 = false, so the button stays enabled and entries can be removed past min.
• with only max set (Schema.array(X).max(3)) — at three entries isMin is
  3 >= 3 = true, so the button is disabled and entries cannot be removed at all,
  even though there is no lower bound.

min/max are the only two bounds and isMax already reads max, so the fix is the
comparison operand.