remove min-ratio setting and enforcement

- Drop minRatio parameter from container.adjustBoundary; guard is now
  newLeft/newRight <= 0 (i.e. only prevent a pane from inverting)
- Remove _getMinRatio() helper and all call sites in windowManager.ts
- Remove Window Sizing preferences group and min-window-size-percent
  spin button from prefs.ts
- Remove min-window-size-percent GSettings key from schema XML

schemas/org.gnome.shell.extensions.aerospike.gschema.xml

@@ -55,12 +55,5 @@
             <description>Resets all window size ratios in the active window's container to equal splits</description>
         </key>
 
-        <key name="min-window-size-percent" type="d">
-            <default>0.10</default>
-            <range min="0.01" max="0.49"/>
-            <summary>Minimum window size percentage</summary>
-            <description>Minimum fraction of a container that any single window may occupy when resizing boundaries</description>
-        </key>
-
     </schema>
 </schemalist>