Use correct case for aggregate shapes in table

[gosar]

Background

Updates the table in https://smithy.io/2.0/spec/model.html#shape-types for Aggregate types to use the casing of the actual shape names, like list instead of List.

Note, this doesn't change the heading on the page https://smithy.io/2.0/spec/aggregate-types.html#list which is still List. We could consider changing the headings to match the shape name too, like for simple types, though we use uppercase for service types. Additional to this PR, if we want to change the headings to match the shape name, can do that separately.

Testing

cd docs
make install
make html
open build/html/2.0/index.html

Ran above and verified table has lower case in type column.

Links

• Links to additional context, if necessary
• Issue #, if applicable (see here for a list of keywords to use for linking issues)

---

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.