Update docs/embedded/zephyr.mdx

Co-authored-by: Marten Lohstroh <[email protected]>

Author: erlingrj

docs/embedded/zephyr.mdx

@@ -215,7 +215,7 @@ west build -t run
 ```
 
 # Timing-precision
-There exists two different Zephyr implementations of the LF timing API. The
+There exist two different Zephyr implementations of the LF timing API. The
 default is based on the [Zephyr Kernel
 Timing](https://docs.zephyrproject.org/latest/kernel/services/timing/clocks.html).
 It is simple and supported on all boards with Zephyr support. However it is not