Fix bound math on mass screenshot verb (#5814)

# About the pull request

This PR is a follow up to #5165 fixing the mass screenshot verb. See
screenshots section below for comparison.

As far as I can tell the max x and max y is unchanged from before to
now, so its just the concept of a min x and y that was handled
incorrectly in how this verb was modified:
Before that PR: `cur_level.x_bounds: 175 cur_level.y_bounds: 226`
After that PR: `MAP_MAXX: 175 MAP_MINX: 1 MAP_MAXY: 226 MAP_MINY: 1`

# Explain why it's good for the game
Bug fixes are good.

# Testing Photographs and Procedure
<details>
<summary>Screenshots & Videos</summary>

Before this PR:

![before](https://github.com/cmss13-devs/cmss13/assets/76988376/a5b44164-b621-423b-af05-af20bd28fb57)

After this PR:

![after](https://github.com/cmss13-devs/cmss13/assets/76988376/da8e9a5a-3bae-4a5e-a918-6daf9dc44f37)

</details>


# Changelog
:cl: Drathek
fix: Fixed the Mass Screenshot Debug verb bounds
/:cl:

code/modules/admin/verbs/debug.dm

@@ -117,8 +117,8 @@
 		var/datum/space_level/cur_level = SSmapping.z_list[cur_z]
 		cur_x += cur_level.bounds[MAP_MINX] - 1
 		cur_y += cur_level.bounds[MAP_MINY] - 1
-		width = cur_level.bounds[MAP_MAXX] - cur_level.bounds[MAP_MINX] - half_chunk_size + 1
-		height = cur_level.bounds[MAP_MAXY] - cur_level.bounds[MAP_MINY] - half_chunk_size + 1
+		width = cur_level.bounds[MAP_MAXX] - cur_level.bounds[MAP_MINX] - half_chunk_size + 3
+		height = cur_level.bounds[MAP_MAXY] - cur_level.bounds[MAP_MINY] - half_chunk_size + 3
 	else
 		width = world.maxx - half_chunk_size + 2
 		height = world.maxy - half_chunk_size + 2