encoding/openapi: link to correct upstream doc

This updates two links in the encoding/openapi package documentation to
reflect a change in a third-party's default git branch name, and a
different HTML fragment identifier used by their reference
documentation.

Signed-off-by: Jonathan Matthews <github@hello.jonathanmatthews.com>
Change-Id: Ie566aee5092eba91ca34e5a38f5968dffacfc1ce
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1194552
Reviewed-by: Paul Jolly <paul@myitcv.io>
TryBot-Result: CUEcueckoo <cueckoo@cuelang.org>

encoding/openapi/doc.go

@@ -17,5 +17,5 @@
 //
 // It currently handles OpenAPI Schema components only.
 //
-// See https://github.com/OAI/OpenAPI-Specification/blob/master/versions/3.0.0.md#schemaObject.
+// See https://github.com/OAI/OpenAPI-Specification/blob/main/versions/3.0.0.md#schema-object
 package openapi

encoding/openapi/types.go

@@ -25,7 +25,7 @@ import (
 	"cuelang.org/go/cue/token"
 )
 
-// See https://github.com/OAI/OpenAPI-Specification/blob/master/versions/3.0.0.md#data-types
+// See https://github.com/OAI/OpenAPI-Specification/blob/main/versions/3.0.0.md#data-types
 var cueToOpenAPI = map[string]string{
 	"int32": "int32",
 	"int64": "int64",