[class.mem.general] Remove stray closing parenthesis (cplusplus#7880)

Author: Andreas-Krug

source/classes.tex

@@ -624,7 +624,7 @@
 \end{note}
 
 \pnum
-The optional \grammarterm{function-contract-specifier-seq}\iref{dcl.contract.func})
+The optional \grammarterm{function-contract-specifier-seq}\iref{dcl.contract.func}
 in a \grammarterm{member-declarator}
 shall be present only if
 the \grammarterm{declarator} declares a function.