[DOCS] Fix unreachable links in the document

## What changes were proposed in this pull request?

Recently, I found two unreachable links in the document and fixed them.
Because of small changes related to the document, I don't file this issue in JIRA but please suggest I should do it if you think it's needed.

## How was this patch tested?

Tested manually.

Author: Kousuke Saruta <[email protected]>

Closes apache#19195 from sarutak/fix-unreachable-link.

Author: sarutak

docs/building-spark.md

@@ -111,7 +111,7 @@ should run continuous compilation (i.e. wait for changes). However, this has not
 extensively. A couple of gotchas to note:
 
 * it only scans the paths `src/main` and `src/test` (see
-[docs](http://scala-tools.org/mvnsites/maven-scala-plugin/usage_cc.html)), so it will only work
+[docs](http://davidb.github.io/scala-maven-plugin/example_cc.html)), so it will only work
 from within certain submodules that have that structure.
 
 * you'll typically need to run `mvn install` from the project root for compilation within

docs/rdd-programming-guide.md

@@ -604,7 +604,7 @@ before the `reduce`, which would cause `lineLengths` to be saved in memory after
 Spark's API relies heavily on passing functions in the driver program to run on the cluster.
 There are two recommended ways to do this:
 
-* [Anonymous function syntax](http://docs.scala-lang.org/tutorials/tour/anonymous-function-syntax.html),
+* [Anonymous function syntax](http://docs.scala-lang.org/tour/basics.html#functions),
   which can be used for short pieces of code.
 * Static methods in a global singleton object. For example, you can define `object MyFunctions` and then
   pass `MyFunctions.func1`, as follows: