Kills The British Empire (#3051)

<!-- Write **BELOW** The Headers and **ABOVE** The comments else it may
not be viewable. -->
<!-- You can view Contributing.MD for a detailed description of the pull
request process. -->

## About The Pull Request
Replaces the british mug in the loadout with a generic mug.
<!-- Describe The Pull Request. Please be sure every change is
documented or this can delay review and even discourage maintainers from
merging your PR! -->

## Why It's Good For The Game
The British aren't real. They can't hurt you. Not after a certain
Solarian captain shattered a priceless artifact, at least.
<!-- Please add a short description of why you think these changes would
benefit the game. If you can't justify it in words, it might not be
worth adding. -->

## Changelog

:cl:
tweak: mugs referencing an ancient terran empire have been confiscated
by the confederation. Please enjoy your complementary, generic mug in
compensation
/:cl:

<!-- Both :cl:'s are required for the changelog to work! You can put
your name to the right of the first :cl: if you want to overwrite your
GitHub username as author ingame. -->
<!-- You can use multiple of the same prefix (they're only used for the
icon ingame) and delete the unneeded ones. Despite some of the tags,
changelogs should generally represent how a player might be affected by
the changes rather than a summary of the PR's contents. -->

code/modules/client/loadout/loadout_general.dm

@@ -36,7 +36,7 @@
 
 /datum/gear/mug
 	display_name = "coffee mug"
-	path = /obj/item/reagent_containers/food/drinks/britcup
+	path = /obj/item/reagent_containers/food/drinks/mug
 
 /datum/gear/rilena_mug
 	display_name = "coffee mug, rilena"