Minor corrections to Cookbook examples.
Minor corrections to Cookbook examples.

* Rename `hash` rule in Computed dependencies section since the name of the
  rule conflicts with the Skylark function of the same name.
* Fix styling in some examples.

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MOS_MIGRATED_REVID=132588578

davidzchen/bazel-website,bazelbuild/bazel-website,davidzchen/bazel-website,davidzchen/bazel-website,bazelbuild/bazel-website,davidzchen/bazel-website,bazelbuild/bazel-website