fix(gatsby): don't ignore SOURCE_FILE_CHANGED event (#30127) (#30129)

(cherry picked from commit f6d1c09)

Co-authored-by: Michal Piechowiak <misiek.piechowiak@gmail.com>

Author: GatsbyJS Bot

packages/gatsby/src/state-machines/develop/index.ts

@@ -276,8 +276,6 @@ const developConfig: MachineConfig<IBuildContext, any, AnyEventObject> = {
         ADD_NODE_MUTATION: {
           actions: `callApi`,
         },
-        // Ignore, because we're about to extract them anyway
-        SOURCE_FILE_CHANGED: undefined,
       },
       invoke: {
         src: `reloadData`,