Delete chapter 4.5
Delete chapter 4.5

Deleting chapter 4.5 per issue #16

wavebeem/website-squiggle,squiggle-lang/squiggle-lang.org,wavebeem/website-squiggle,wavebeem/website-squiggle,squiggle-lang/squiggle-lang.org,wavebeem/website-squiggle,squiggle-lang/squiggle-lang.org,squiggle-lang/squiggle-lang.org