internal/lsp: fix bug in diagnostics for watched changed files

I accidentally copy-pasted code in CL 196019.

Change-Id: I092bfd745182f1c35e0540f080f139c4ced15776
Reviewed-on: https://go-review.googlesource.com/c/tools/+/196277
Run-TryBot: Rebecca Stambler <rstambler@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Cottrell <iancottrell@google.com>
diff --git a/internal/lsp/watched_files.go b/internal/lsp/watched_files.go
index 08758d7..5a70029 100644
--- a/internal/lsp/watched_files.go
+++ b/internal/lsp/watched_files.go
@@ -86,7 +86,7 @@
 					}
 					return nil
 				}
-				go s.diagnostics(view, uri)
+				go s.diagnostics(view, otherFile.URI())
 			}
 		}
 	}