docking3deffects.ui: Fix typo (lowercase initial) in translatable string

Change-Id: I833c8b8ea8af1c93b1fe6ec3d7887921f2dab285

svx/uiconfig/ui/docking3deffects.ui

@@ -1846,7 +1846,7 @@
                         <property name="visible">True</property>
                         <property name="can_focus">False</property>
                         <property name="xalign">0</property>
-                        <property name="label" translatable="yes">i_ntensity</property>
+                        <property name="label" translatable="yes">I_ntensity</property>
                         <property name="use_underline">True</property>
                         <property name="mnemonic_widget">intensity:0%</property>
                       </object>