Undo apparent accidental @-color replaces in upstream TBA files. (#62)

I am guessing some script or tool used upstream is doing an unsafe
search-and-replace for '@' with TAB, and accidentally changing these.
They seem to have been creeping into the repo for years.

I produced this fix commit automatically with:
  sed -i 's|\t\([bcdgmnoruwyBCDGMRWY]\)|@\1|g' tba/*/*.*
...and then a few files' changes had to be undone.

I looked through all of the rest, and they look like correct fixes.

I also ran all the other letters, and they only make incorrect "fixes".

lib/world/wld/301.wld

@@ -489,10 +489,10 @@ E
 sign warning~
    The sign says:
 Welcome to the Student Ghetto!
-	n
+@n
 Fine $103.50 for carrying open alcohol in the streets.
 Fine $ 53.75 for excessively loud noises.
-	n
+@n
 ENTER AT YOUR OWN RISK!
 ~
 E
@@ -1214,7 +1214,7 @@ plaque plaques~
 E
 sign~
    The sign says:
-	n
+@n
     Gym           -> North
     Arena         -> East
     Locker Rooms  -> West