Pressing `M-.` on ALPHA in
(let ((ALPHA BETA)) ...)
would incorrectly search for ALPHA as a function rather than a variable.
* lisp/progmodes/elisp-mode.el (elisp--xref-infer-namespace): Fix logic.
* test/lisp/progmodes/elisp-mode-tests.el
(elisp-mode-infer-namespace): Add test case.