TBR: devtools: Add '/.jiri' to .gitignore in all repos.
TBR: devtools: Add '/.jiri' to .gitignore in all repos.

Change-Id: I7582db69dcc9fb5b68015144695e08e938c6480f
MultiPart: 7/28
PresubmitTest: none

vanadium/go.devtools,vanadium/go.devtools,vanadium/go.devtools