[css-overflow-4] Rename sections

These are not solely about fragmentation, so use a more generic
phrasing.

Author: frivoal

css-overflow-4/Overview.bs

@@ -812,8 +812,8 @@ Indicating Block-Axis Overflow: the 'block-ellipsis' property</h3>
 	(in which case, it can capture events).
 
 
-<h2 id=fragmentating-overflow>
-Fragmenting Overflow</h2>
+<h2 id=suppressing-excess oldids=fragmentating-overflow>
+Suppressing Excess Content</h2>
 
 <h3 id=line-clamp>
 Limiting Visible Lines: the 'line-clamp' shorthand property</h3>
@@ -1019,7 +1019,7 @@ Forcing a Break After a Set Number of Lines: the 'max-lines' property</h3>
 	</div>
 
 <h3 id="continue">
-Fragmentation of Overflow: the 'continue' property</h3>
+Handling of Excess Content: the 'continue' property</h3>
 
 	<pre class=propdef>
 		Name: continue