Fix joaotavora#488: fix type error in eglot--xref-make-match

Its first argument is passed to xref-make-match, which expects a string
as its SUMMARY argument, but symbol-at-point returns a symbol.

Co-authored-by: João Távora <joaotavora@gmail.com>

* eglot.el (eglot--lsp-xrefs-for-method): use symbol-name.

eglot.el

@@ -1954,7 +1954,8 @@ Try to visit the target file for a richer summary line."
     (eglot--collecting-xrefs (collect)
       (mapc
        (eglot--lambda ((Location) uri range)
-         (collect (eglot--xref-make-match (symbol-at-point) uri range)))
+         (collect (eglot--xref-make-match (symbol-name (symbol-at-point))
+                                          uri range)))
        (if (vectorp response) response (list response))))))
 
 (cl-defun eglot--lsp-xref-helper (method &key extra-params capability )