homeworld/grub: Remove Debian major version number

This seems to have been missed when the version number was removed from
other theme components during #989822.

Helps: #989822
Signed-off-by: Simon McVittie <smcv@debian.org>

homeworld-theme/grub/grub-16x9.svg

@@ -297,15 +297,7 @@
    height="10.589"
    id="rect75" />
 		
-			<text
-   transform="scale(1.0000015)"
-   fill="#ffffff"
-   font-family="PopplLaudatio-Condensed"
-   font-size="13.0386px"
-   id="text77"
-   x="211.00555"
-   y="458.34839"
-   style="fill:#062d58;fill-opacity:1;stroke-width:1">11</text>
+			
 	</g><rect
    x="829.901"
    y="516.50867"

homeworld-theme/grub/grub-4x3.svg

@@ -236,14 +236,7 @@
    height="10.589"
    id="rect75" />
 		
-			<text
-   fill="#ffffff"
-   font-family="PopplLaudatio-Condensed"
-   font-size="13.0386px"
-   id="text77"
-   x="103.00591"
-   y="458.41022"
-   style="fill:#062d58;fill-opacity:1;stroke-width:1">11</text>
+			
 	</g>
 	
 		<rect