docs: typo

docs/derived.tex

@@ -16,7 +16,7 @@ Now we define:
   \CInv{\gname}{\namesp}{\prop} \eqdef{}& \knowInv\namesp{\prop \lor \ownGhost\gname{1}}
 \end{align*}
 
-It is then straight-forward to prove:
+It is then straight forward to prove:
 \begin{mathpar}
   \inferH{CInv-new}{}
   {\later\prop \vs[\bot] \Exists \gname. \CInvTok\gname{1} * \always\CInv\gname\namesp\prop}