[lldb][Docs] Update links in Data Formatter section (llvm#66474)

Neither actually linked anywhere, but I did find a good target for the
introduction.

For the architecture side I don't see a page that would fit, so I've
just removed the sentence.

Author: DavidSpickett

lldb/docs/resources/overview.rst

@@ -80,8 +80,8 @@ wide variety of classes are implemented:
 - Source manager
 - Value objects
 
-Dataformatters
---------------
+Data Formatters
+---------------
 
 A collection of classes that implement the data formatters subsystem.
 
@@ -92,9 +92,7 @@ layers to the implementation: DataVisualization at the highest end of the
 spectrum, backed by classes implementing individual formatters, matching rules,
 etc.
 
-For a general user-level introduction to data formatters, you can look here.
-
-More details on the architecture are to be found here.
+For an introduction to data formatters, see :doc:`/use/variable`.
 
 Expression
 ----------