[GLib] Must set GI_TYPELIB_PATH in verify-release-candidate.sh

[asfimport]

This is a new necessary step when validating a release candidate

Reporter: Wes McKinney / @wesm
Assignee: Wes McKinney / @wesm

PRs and other links:

• GitHub Pull Request #1417

_{Note: This issue was originally created as ARROW-1917. Please see the migration documentation for further details.}

[asfimport]

Wes McKinney / @wesm:
Issue resolved by pull request 1417
#1417