_content: fix package name in branch module image

The v2 branch should use the name "package1" for its example package, to
be consistent with the v1 branch and the subsequent documentation.

I edited the image in GIMP and exported with maximal compression, then
used optipng to optimize the resulting file, but still did not quite
achieve the previous level of compression.

Fixes golang/go#59948

Change-Id: I64d9d4d21e5bf79731cdd02401420bd81e2bb33d
Reviewed-on: https://go-review.googlesource.com/c/website/+/492475
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Robert Findley <rfindley@google.com>
Reviewed-by: Jamal Carvalho <jamal@golang.org>
diff --git a/_content/doc/modules/images/v2-branch-module.png b/_content/doc/modules/images/v2-branch-module.png
index ad7b60f..cce6b7c 100644
--- a/_content/doc/modules/images/v2-branch-module.png
+++ b/_content/doc/modules/images/v2-branch-module.png
Binary files differ