doc: Fix missing whitespace in pg_restore documentation.

Previously, a space was missing between "<option>--exclude-schema</option>"
and "for" in the pg_restore documentation. This commit fixes the typo by
adding the missing whitespace.

Back-patch to v17 where the typo was added.

Author: Lele Gaifax <lele@metapensiero.it>
Reviewed-by: Fujii Masao <masao.fujii@gmail.com>
Discussion: https://postgr.es/m/87lds3ysm0.fsf@metapensiero.it
Backpatch-through: 17

doc/src/sgml/ref/pg_restore.sgml

@@ -198,7 +198,7 @@ PostgreSQL documentation
         or included from restore. The patterns are interpreted according to the
         same rules as
         <option>-n</option>/<option>--schema</option> for including objects in schemas,
-        <option>-N</option>/<option>--exclude-schema</option>for excluding objects in schemas,
+        <option>-N</option>/<option>--exclude-schema</option> for excluding objects in schemas,
         <option>-P</option>/<option>--function</option> for restoring named functions,
         <option>-I</option>/<option>--index</option> for restoring named indexes,
         <option>-t</option>/<option>--table</option> for restoring named tables