go/analysis: fix typos and update documentation

Change-Id: I48187fcb1eedd5b94d7b6b2db1ae11009bab23a2
Reviewed-on: https://go-review.googlesource.com/c/157299
Reviewed-by: Alan Donovan <adonovan@google.com>

go/analysis/doc.go

@@ -246,7 +246,7 @@ An Analyzer that uses facts must declare their types:
 
 	var Analyzer = &analysis.Analyzer{
 		Name:       "printf",
-		FactTypes: []reflect.Type{reflect.TypeOf(new(isWrapper))},
+		FactTypes: []analysis.Fact{new(isWrapper)},
 		...
 	}
 

go/analysis/passes/inspect/inspect.go

@@ -8,7 +8,11 @@
 //
 // Example of use in another analysis:
 //
-//	import "golang.org/x/tools/go/analysis/passes/inspect"
+//	import (
+//		"golang.org/x/tools/go/analysis"
+//		"golang.org/x/tools/go/analysis/passes/inspect"
+//		"golang.org/x/tools/go/ast/inspector"
+//	)
 //
 //	var Analyzer = &analysis.Analyzer{
 //		...