cloud/storage/b2cs: delete cmd/upspinserver-b2cs/upspinserver-b2cs

I accidentally uploaded the binary upspinserver-b2cs at the last commit.
Sorry about that.

Change-Id: Icbb80874cb96fb683bd723b16619a1a4aa9f5cf3
Reviewed-on: https://upspin-review.googlesource.com/18120
Reviewed-by: Rob Pike <r@golang.org>
diff --git a/cmd/upspinserver-b2cs/upspinserver-b2cs b/cmd/upspinserver-b2cs/upspinserver-b2cs
deleted file mode 100755
index 54c2135..0000000
--- a/cmd/upspinserver-b2cs/upspinserver-b2cs
+++ /dev/null
Binary files differ