fix eslint rule name

ha404 · ljharb · commit bfda3c0c6f89 · 2017-12-13T00:52:31.000-08:00
diff --git a/docs/rules/prefer-default-export.md b/docs/rules/prefer-default-export.md
@@ -1,4 +1,4 @@
-# prefer-default-export
+# import/prefer-default-export
 
 When there is only a single export from a module, prefer using default export over named export.
 

Original file line number	Diff line number	Diff line change
`@@ -1,4 +1,4 @@`
`1`		`-# prefer-default-export`
	`1`	`+# import/prefer-default-export`
`2`	`2`
`3`	`3`	`When there is only a single export from a module, prefer using default export over named export.`
`4`	`4`