remove repetitive words (#2046)

Signed-off-by: studystill <chenghuiyue@outlook.com>

examples/readme.rs

@@ -1,7 +1,7 @@
 //! The example from the readme!
 //!
 //! This example demonstrates how to create a simple counter app with dioxus. The `Signal` type wraps inner values,
-//! making them `Copy`, allowing them to be freely used in closures and and async functions. `Signal` also provides
+//! making them `Copy`, allowing them to be freely used in closures and async functions. `Signal` also provides
 //! helper methods like AddAssign, SubAssign, toggle, etc, to make it easy to update the value without running
 //! into lock issues.