samples: blinky: Remove incorrect integration platform

Remove the integration platform, which was with a platform not listed in
the supported platforms.

Signed-off-by: David Brown <[email protected]>

Author: d3zd3z

samples/blinky/sample.yaml

@@ -17,5 +17,3 @@ tests:
     filter: dt_enabled_alias_with_parent_compat("led0", "gpio-leds")
     depends_on: gpio
     harness: led
-    integration_platforms:
-      - frdm_k64f