Minor documentation fixes

* Remove duplicated Interface Kit description.
* Fixed links, a typo, inconsistent page names.

Change-Id: I38e5943f31bf30870d33f02a97b4ef899222ec36
Reviewed-on: https://review.haiku-os.org/c/haiku/+/4854
Tested-by: Commit checker robot <[email protected]>
Reviewed-by: Adrien Destugues <[email protected]>

docs/user/interface/_interface_intro.dox

@@ -30,13 +30,13 @@
 	is based around the BLayoutItem and BLayout classes. These classes will
 	take care of making sure all your GUI widgets end up where you want them,
 	with enough space to be useful. You can start learning the Layout API 
-	by reading the \link layout_intro introduction \endlink.
+	by reading the \ref layout_intro.
 
-	\section Coordinate spaces
+	\section coordinatespaces Coordinate spaces
 
-	All APIs using coordinates (such as \link BRect or \link BPoint ) refer to
-	a specific space where these coordinates are interpreted. \link BView and
-	\link BWindow provide various conversion function to translate coordinates
+	All APIs using coordinates (such as BRect or BPoint) refer to
+	a specific space where these coordinates are interpreted. BView and
+	BWindow provide various conversion function to translate coordinates
 	between different spaces, as needed, or provide separate methods such as
 	BView Bounds() and Frame(), returning results in different spaces as needed.
 

docs/user/interface/_layout_intro.dox

@@ -9,7 +9,7 @@
 
 
 /*!
-	\page layout_intro Introducing the Layout API.
+	\page layout_intro Introduction to the Layout API
 
 	Haiku's Layout API is centered around the BLayoutItem and BLayout classes.
 	The BLayoutItem class represents thing that can be managed by a BLayout,

docs/user/interface/layout_tips.dox

@@ -1,5 +1,5 @@
 /*!
-	\page layout_tips
+	\page layout_tips Layout API tips
 
 	\section layout_window_tips BWindow Tips