Wording change: Dedupe dictionary member type and default definitions (#526)

Bikeshed automatically annotates dictionary members with types and
defaults, so repeating that in the prose is extra work and extra
noise. Remove both and reword as needed. For #483

Also:

- Simplify text by removing "Specifies" from most definition prose.
- Replace "sequence" with "list" in prose.
- Consistently give list member definitions using *[ ... *] styling.
- Document the above in coding conventions.

Author: inexorabletash

SpecCodingConventions.md

@@ -76,6 +76,7 @@ Example:
 * Bikeshed will automatically style linked terms appropriately, for example Web IDL types show up as `code`. Try to avoid manual styling wherever possible; if you're not getting the style you expect, you may have incorrect definitions or links.
 * Outside of examples, which should be appropriately styled automatically, literals such as numbers within spec prose are not JavaScript values and should not be styled as code.
 * Strings used internally (e.g. operator names) should not be styled as code.
+* When concisely defining a list's members or a tensor's layout, use the syntax `*[ ... ]*` (e.g. _"nchw" means the input tensor has the layout *[batches, inputChannels, height, width]*_)
 
 
 ### Algorithms