docs: update mitex version in README example

Author: OrangeX4

README.md

@@ -22,7 +22,7 @@ PS: `#set math.equation(numbering: "(1)")` is also valid for MiTeX.
 Following is [a simple example](https://github.com/mitex-rs/mitex/blob/main/packages/mitex/examples/example.typ) of using MiTeX in Typst:
 
 ```typst
-#import "@preview/mitex:0.2.4": *
+#import "@preview/mitex:0.2.6": *
 
 Write inline equations like #mi(`x`).