Fix typo

platformio_override.sample.ini

@@ -34,7 +34,7 @@ lib_deps = ${esp8266.lib_deps}
 build_unflags = ${common.build_unflags}
 build_flags = ${common.build_flags} ${esp8266.build_flags}
 ;
-; *** To use the below defines/overrides, copy and paste each onto it's own line just below build_flags in the section above.
+; *** To use the below defines/overrides, copy and paste each onto its own line just below build_flags in the section above.
 ; 
 ; Set a release name that may be used to distinguish required binary for flashing
 ;   -D WLED_RELEASE_NAME=\"ESP32_MULTI_USREMODS\"