Removed type definition files and refinements

docs/_posts/2021-03-01-luau-recap-february-2021.md

@@ -17,10 +17,6 @@ The Luau parser now recovers from errors, which means, for example, we can give
 
 ![A type error after a syntax error]({{ site.url }}{{ site.baseurl }}/assets/images/type-error-after-syntax-error.png)
 
-## Type definition files
-
-Developers familiar with TypeScript will know all about `.d.ts` declaration files, and now they're in Luau too! A Luau *type definition file* contains just the types for a library, not its implementation. They're very useful when you're interfacing to an existing third-party library, and want to use it in a type-safe way. Now you can declare the types it exports, without having to look at its source code.
-
 ## Type assertions
 
 The Luau type checker can't know everything about your code, and sometimes it will produce type errors even when you know the code is correct. For example, sometimes the type checker can't work out the intended types, and gives a message such as "Unknown type used... consider adding a type annotation".
@@ -31,12 +27,6 @@ Previously the only way to add an annotation was to put it on the *declaration*
 
 !["A type assertion y:any"]({{ site.url }}{{ site.baseurl }}/assets/images/type-annotation-provided.png)
 
-## Improved type refinements
-
-Type refinements are used when a check is made on the dynamic type of a variable. Luau knows the static type during type-checking, but the dynamic type might be a refinement of the static type (or it might not, that's why we're checking it). For example, if the static type of `x` is `any`, then we might check that it's a number before incrementing it.
-
-!["A type refinement type(x) == "number"]({{ site.url }}{{ site.baseurl }}/assets/images/type-refinement-in-action.png)
-
 ## Performance improvements
 
 We've made quite a few performance improvements to the Luau bytecode interpreter.