go/callgraph/vta: fix package doc

A blank line prevented go doc from picking up the package doc.

Change-Id: I40ddb95d0e38ee0809a852205f399d18f9d68be3
Reviewed-on: https://go-review.googlesource.com/c/tools/+/391514
Trust: Hyang-Ah Hana Kim <hyangah@gmail.com>
Run-TryBot: Hyang-Ah Hana Kim <hyangah@gmail.com>
gopls-CI: kokoro <noreply+kokoro@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Zvonimir Pavlinovic <zpavlinovic@google.com>

go/callgraph/vta/vta.go

@@ -51,7 +51,6 @@
 // it may have. This information is then used to construct the call graph.
 // For each unresolved call site, vta uses the set of types and functions
 // reaching the node representing the call site to create a set of callees.
-
 package vta
 
 import (