Current Org-mode does not work with Emacs 27

[Yasushi SHOJI]

Hi all,

 It appears that Emacs 27 lacks the optional argument for
`get-buffer-create`, while `org-element-parse-secondary-string`
relies on it. This problem was introduced by the commit 37d6bde27fe2.

Additionally, `org-id-find-id-in-file` also uses `get-buffer-create`
with a second argument, but it checks the function and has a condition
to call it with or without the argument.

Given that `org-compat.el` already contains compatibility functions
for different Emacs versions, should we create one for
`get-buffer-create` to address this issue? Since `org-compat.el`
provides compatibility layers for Emacs 26.1 and later, it's
reasonable to assume that Org mode still supports Emacs 27?

Thanks,
-- 
           yashi