internal/lsp/cache: fix InDir error comment

Change-Id: I06b5cfe3053a5ebfc45e34c4b8aeeb10393ce581
Reviewed-on: https://go-review.googlesource.com/c/tools/+/269397
Reviewed-by: Rebecca Stambler <rstambler@golang.org>
Trust: Rebecca Stambler <rstambler@golang.org>
Trust: Robert Findley <rfindley@google.com>
Run-TryBot: Rebecca Stambler <rstambler@golang.org>
gopls-CI: kokoro <noreply+kokoro@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
diff --git a/internal/lsp/source/util.go b/internal/lsp/source/util.go
index b3d87f9..72b074a 100644
--- a/internal/lsp/source/util.go
+++ b/internal/lsp/source/util.go
@@ -443,8 +443,6 @@
 }
 
 // InDir checks whether path is in the file tree rooted at dir.
-// If so, InDir returns an equivalent path relative to dir.
-// If not, InDir returns an empty string.
 // InDir makes some effort to succeed even in the presence of symbolic links.
 //
 // Copied and slightly adjusted from go/src/cmd/go/internal/search/search.go.