Manual: fix name of variable containing conditional forecast instruments

It should have been done in commit b9af92eb.

By the way, fix a font decoration issue.

[skip ci]

doc/manual/source/the-model-file.rst

@@ -11731,9 +11731,9 @@ the :comm:`bvar_forecast` command.
             oo_.conditional_forecast.uncond.FORECAST_MOMENT.VARIABLE_NAME
-    .. matvar:: forecasts.instruments
-        Variable set by the ``conditional_forecast command``. Stores
+    .. matvar:: oo_.conditional_forecast.instruments
+        Variable set by the ``conditional_forecast`` command. Stores
         the names of the exogenous instruments.