builder/services.go: Update proxyd flag

Required change to match
https://vanadium-review.googlesource.com/#/c/5330/

MultiPart: 2/2
Change-Id: Ifd108947764c20a9a2c43596cb8461637efb5eb1
1 file changed
tree: 571ffcb1aab8ed3c9e877e3b83382555809c99b7
  1. client/
  2. go/
  3. pgbundle/
  4. .gitignore