format: Relax reserved keywords

Builtin types, and the word `as` do not need to be reserved, as such, we can safely remove them

Author: huwaireb

design/mvp/WIT.md

@@ -629,26 +629,13 @@ keyword ::= 'use'
           | 'type'
           | 'resource'
           | 'func'
-          | 'u8' | 'u16' | 'u32' | 'u64'
-          | 's8' | 's16' | 's32' | 's64'
-          | 'float32' | 'float64'
-          | 'char'
           | 'record'
           | 'enum'
           | 'flags'
           | 'variant'
           | 'union'
-          | 'bool'
-          | 'string'
-          | 'option'
-          | 'list'
-          | 'result'
-          | 'as'
           | 'static'
           | 'interface'
-          | 'tuple'
-          | 'future'
-          | 'stream'
           | 'world'
           | 'import'
           | 'export'