chore(gatsby-source-filesystem): remove outdated comments (gatsbyjs#9431

)

The corresponding code was removed in gatsbyjs#8859.

src/gatsby-node.js

@@ -6,15 +6,7 @@ const { Machine } = require(`xstate`)
 const { createFileNode } = require(`./create-file-node`)
 
 /**
- * Create a state machine to manage Chokidar's not-ready/ready states and for
- * emitting file system events into Gatsby.
- *
- * On the latter, this solves the problem where if you call createNode for the
- * same File node in quick succession, this can leave Gatsby's internal state
- * in disarray causing queries to fail. The latter state machine tracks when
- * Gatsby is "processing" a node update or when it's "idle". If updates come in
- * while Gatsby is processing, we queue them until the system returns to an
- * "idle" state.
+ * Create a state machine to manage Chokidar's not-ready/ready states.
  */
 const createFSMachine = () =>
   Machine({