Spec: revert unnecessary change in overview.tex

spec/overview.tex

@@ -39,13 +39,11 @@ \subsection{Opening the head}
 locks (on the mainchain) the UTxOs that the party wants to commit to the head,
 or deliberately acknowledges to commit nothing.
 
-The commit transactions are subsequently collected by the \mtxCCom{}
-transaction causing a transition from $\stInitial$ to $\stOpen$. Once the
-$\stOpen$ state is confirmed, the head members start running the off-chain head
-protocol, which evolves the initial UTxO set (the union over all UTxOs
-committed by all head members) independently of the mainchain. Head member can
-also decide to take some UTxO they own out of the Head and make it available on
-main chain. We call this action decrement. For the case where some head members
+The commit transactions are subsequently collected by the \mtxCCom{} transaction
+causing a transition from $\stInitial$ to $\stOpen$. Once the $\stOpen$ state is
+confirmed, the head members start running the off-chain head protocol, which
+evolves the initial UTxO set (the union over all UTxOs committed by all head
+members) independently of the mainchain. For the case where some head members
 fail to post a \mtxCom{} transaction, the head can be aborted by going directly
 from $\stInitial$ to $\stFinal$.