CTR fix additional broken links in reference doc

Author: xiazcy

docs/src/reference/intro.asciidoc

@@ -23,8 +23,8 @@ from which to spawn more detailed accounts of specific topics and a target to wh
 The Reference Documentation makes some general assumptions about the reader:
 
 1. They have a sense of what a graph is - not sure? see link:http://kelvinlawrence.net/book/Gremlin-Graph-Guide.html#whygraph[Practical Gremlin - Why Graph?]
-1. They know what it means for a graph system to be TinkerPop-enabled - not sure? see link:https://tinkerpop.apache.org/providers.html[TinkerPop-enabled Providers]
-1. They know what the role of Gremlin is - not sure? see link:link:https://tinkerpop.apache.org/gremlin.html[Introduction to Gremlin]
+2. They know what it means for a graph system to be TinkerPop-enabled - not sure? see link:https://tinkerpop.apache.org/providers.html[TinkerPop-enabled Providers]
+3. They know what the role of Gremlin is - not sure? see link:https://tinkerpop.apache.org/gremlin.html[Introduction to Gremlin]
 
 Given those assumptions, it's possible to dive more quickly into the details without spending a lot of time repeating
 what is written elsewhere.

docs/src/reference/preface.asciidoc

@@ -90,4 +90,4 @@ realized realizations are just as real. For that is -- The TinkerPop.
 image::gremlintron.png[width=400]
 
 NOTE: For more information about differences between TinkerPop 3.x and earlier versions, please see the
-link:https://tinkerpop.apache.org/docs/x.y.z/upgrade/#appendix
+link:https://tinkerpop.apache.org/docs/x.y.z/upgrade/#appendix[appendix].