Fix typos in LWIP README

Author: earlephilhower

cores/rp2040/lwip/README.md

@@ -1,7 +1,7 @@
 # Overview
 
 This directory #include points to the SDK's LWIP implementation.  We remove
-any prebuilt LWIP files at the makelibpico and allow the IDE to semect
+any prebuilt LWIP files at the makelibpico and allow the IDE to select
 custom definitions for the build at app compile time.  This removes the
 need for multiple libraries to be built and distributed for things like IPV6
 or large buffers.