org-manual: Small fixes

* doc/org-manual.org (Handling Links): Update variable
`org-id-link-to-org-use-id', which was changed in v7.9.2.

TINYCHANGE

doc/org-manual.org

@@ -3252,12 +3252,12 @@ current buffer:
      points to the target.  Otherwise it points to the current
      headline, which is also the description[fn:30].
 
-     #+vindex: org-link-to-org-use-id
+     #+vindex: org-id-link-to-org-use-id
      #+cindex: @samp{CUSTOM_ID}, property
      #+cindex: @samp{ID}, property
      If the headline has a =CUSTOM_ID= property, store a link to this
      custom ID.  In addition or alternatively, depending on the value
-     of ~org-link-to-org-use-id~, create and/or use a globally unique
+     of ~org-id-link-to-org-use-id~, create and/or use a globally unique
      =ID= property for the link[fn:31].  So using this command in Org
      buffers potentially creates two links: a human-readable link from
      the custom ID, and one that is globally unique and works even if