adjust invisible grammar

combat.tex

@@ -61,9 +61,9 @@ In the latter, blades clash but nobody gets hurt.
 \index{Damage}
 
 If you hit, roll $1D6$ plus your Strength Bonus to determine Damage.
-The Damage is then taken off the enemy's \gls{hp}.
-Everyone has a number of \gls{hp} to withstand Damage.
-When they reach 0 \gls{hp}, they fall over.
+The Damage is then taken off the enemy's \glspl{hp}.
+Everyone has a number of \glspl{hp} to withstand Damage.
+When they reach 0 \glspl{hp}, they fall over.
 
 \subsubsection{Stacking Damage}
 \index{Combat!Stacking Damage}