ox-texinfo: Remove spurious blank line in src block export

* lisp/ox-texinfo.el (org-texinfo-src-block): Remove spurious newline
  character as `org-export-format-code-default' already makes sure the
  string returned will end with a single one.

Thanks to Frank Fischer for reporting it.

lisp/ox-texinfo.el

@@ -1405,11 +1405,11 @@ contextual information."
     (cond
      ;; Case 1.  Lisp Block
      (lisp-p
-      (format "@lisp\n%s\n@end lisp"
+      (format "@lisp\n%s@end lisp"
 	      (org-export-format-code-default src-block info)))
      ;; Case 2.  Other blocks
      (t
-      (format "@example\n%s\n@end example"
+      (format "@example\n%s@end example"
 	      (org-export-format-code-default src-block info))))))
 
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