Update mkdocs/docs/expression-dsl.md

Co-authored-by: Fokko Driesprong <[email protected]>

Author: norton120

mkdocs/docs/expression-dsl.md

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 # Expression DSL
 
 The PyIceberg library provides a powerful expression DSL (Domain Specific Language) for building complex row filter expressions. This guide will help you understand how to use the expression DSL effectively. This DSL allows you to build type-safe expressions for use in the `row_filter` scan argument.