scope: Don't place AM_CONDITIONAL inside a shell condition

This is not valid, because the AM_CONDITIONAL has to be known by
Automake in all cases.  Automake is smart enough to detect it if used
in a AutoShell conditional (like AS_IF/AS_CASE/...), but can't work any
magic inside a pure shell conditional (if/case/...).

So, move the AM_CONDITIONAL outside the conditional, as the value is
already conditional anyway.

build/scope.m4

@@ -11,13 +11,13 @@ AC_DEFUN([GP_CHECK_SCOPE],
 
             GP_CHECK_GTK3([vte_package=vte-2.91], [vte_package="vte >= 0.17"])
             GP_CHECK_PLUGIN_DEPS([scope], [VTE], [$vte_package])
-            AM_CONDITIONAL([GP_VTE291_USED], [test "$enable_scope" != no && test "$vte_package" = vte-2.91])
 
             AC_CHECK_HEADERS([util.h pty.h libutil.h])
             PTY_LIBS="-lutil"
             ;;
     esac
 
+    AM_CONDITIONAL([GP_VTE291_USED], [test "$enable_scope" != no && test "$vte_package" = vte-2.91])
     AC_SUBST(PTY_LIBS)
 
     GP_COMMIT_PLUGIN_STATUS([Scope])