ox-texinfo: Property display images with relative file names

* lisp/ox-texinfo.el (org-texinfo--inline-image): Make sure to remove
leading "./" from file name.

Reported-by: Ramesh Nedunchezian <rameshnedunchezian@outlook.com>
<http://lists.gnu.org/r/emacs-orgmode/2021-04/msg00873.html>

lisp/ox-texinfo.el

@@ -1126,7 +1126,9 @@ current state of the export, as a plist."
 	 (path  (org-element-property :path link))
 	 (filename
 	  (file-name-sans-extension
-	   (if (file-name-absolute-p path) (expand-file-name path) path)))
+	   (if (file-name-absolute-p path)
+               (expand-file-name path)
+             (file-relative-name path))))
 	 (extension (file-name-extension path))
 	 (attributes (org-export-read-attribute :attr_texinfo parent))
 	 (height (or (plist-get attributes :height) ""))