Resize lectern pocket computer textures

This bumps them to be 48x48, which allows them to be downscaled to a
mipmap level of 4. We possibly should bump these to be 64x64 (actual
power of two), but I kinda want to avoid that, as it's so much wasted
space. If this does become a problem, we should probably put these on a
separate atlas instead.

projects/common/src/client/java/dan200/computercraft/client/model/LecternPocketModel.java

@@ -47,8 +47,8 @@ public class LecternPocketModel {
     public static final float TERM_HEIGHT = 14.0f / 32.0f;
 
     // The size of the texture. The texture is 36x36, but is at 2x resolution.
-    private static final int TEXTURE_WIDTH = 36 / 2;
-    private static final int TEXTURE_HEIGHT = 36 / 2;
+    private static final int TEXTURE_WIDTH = 48 / 2;
+    private static final int TEXTURE_HEIGHT = 48 / 2;
 
     private final ModelPart root;