docs: fix DType docs (#3572)

Author: a10y

docs/concepts/dtypes.md

@@ -33,14 +33,14 @@ The following table lists the built-in dtypes in Vortex, each of which can be ma
 | `Null`      | `null`                                      |
 | `Bool`      | `true`, `false`                             |
 | `Primitive` | See [Primitive](#primitive)                 |
-| `UTF8`      | Variable length valid utf-8 encoded strings |
+| `UTF8`      | Variable length valid UTF-8 encoded strings |
 | `Binary`    | Arbitrary variable length bytes             |
 | `Struct`    | See [Struct](#struct)                       |
 | `List`      | See [List](#list)                           |
 | `Extension` | See [Extension](#extension)                 |
 
 :::{note}
-There are additional logical types that Vortex does not yet support, for example fixed-length binary, utf-8, and list
+There are additional logical types that Vortex does not yet support, for example fixed-length binary and list
 types, as well as a map type. These may be added in future versions.
 :::
 
@@ -92,4 +92,4 @@ This section helps those familiar with Apache Arrow to quickly understand the di
   dtypes since that can be composed of other more primitive logical dtypes.
 * In Arrow, tables and record batches have a _schema_ that defines the types of the columns. Vortex makes no
   distinction between a data type and a schema. Columnar data can be stored with a struct dtype, and integer data can
-  be stored equally well without a top-level struct. 
+  be stored equally well without a top-level struct.