org.texi: Fix typo

* doc/org.texi: Remove extra curly bracket.

TINYCHANGE

doc/org.texi

@@ -5020,7 +5020,7 @@ TIMESTAMP_IA @r{The first inactive timestamp in the entry.}
 CLOCKSUM     @r{The sum of CLOCK intervals in the subtree.  @code{org-clock-sum}}
              @r{must be run first to compute the values in the current buffer.}
 CLOCKSUM_T   @r{The sum of CLOCK intervals in the subtree for today.}
-             @r{@code{org-clock-sum-today}} must be run first to compute the}
+             @r{@code{org-clock-sum-today} must be run first to compute the}
              @r{values in the current buffer.}
 BLOCKED      @r{"t" if task is currently blocked by children or siblings}
 ITEM         @r{The headline of the entry.}