doc: fix typo in types tutorial (closed -> close)
doc: fix typo in types tutorial (closed -> close)

Fixes github.com/cuelang/cuelang.org/issues/118

Change-Id: Ib0391938f5182775704b90b4a02393d5f28bd0f8
Reviewed-on: https://cue-review.googlesource.com/c/cue/+/8066
Reviewed-by: Paul Jolly <a027184a55211cd23e3f3094f1fdc728df5e0500@myitcv.org.uk>
Reviewed-by: CUE cueckoo <0f32a827c9a5f00281f936ac78b5ef3ba80a954c@gmail.com>

cuelang/cue