Trim rust-analyzer on-hover (#2627)

Fixes #2613

Author: yyoncho

lsp-mode.el

@@ -4841,7 +4841,7 @@ When language is nil render as markup if `markdown-mode' is loaded."
 
 (cl-defgeneric lsp-clients-extract-signature-on-hover (contents _server-id)
   "Extract a representative line from CONTENTS, to show in the echo area."
-  (car (s-lines (lsp--render-element contents))))
+  (car (s-lines (s-trim (lsp--render-element contents)))))
 
 (defun lsp--render-on-hover-content (contents render-all)
   "Render the content received from 'document/onHover' request.