updated docs

docs/docs/linear_algebra.xml

@@ -906,7 +906,7 @@
       <component>
          <name>distance_to_line</name>
          <file>dlib/geometry.h</file>
-         <spec_file link="true">dlib/geometry/rectangle_abstract.h</spec_file>
+         <spec_file link="true">dlib/geometry/line_abstract.h</spec_file>
          <description>        
             This function takes a line and a <a href="#point">point</a>
             and returns the distance from the line to the point.