info leak: git/.gitconfig still has hardcoded zyyu@umich.edu email

[stanfish06]

git/.gitconfig was missed when PRs #39 and #50 redacted the zyyu/zyu14 identifiers from ssh/config and hpc/ssh/config.

File: git/.gitconfig, line 3

email = zyyu@umich.edu

Fix

Replace with a placeholder comment, matching the established pattern:

-	email = zyyu@umich.edu
+	# email = <your-email>

Note: home-chezmoi/.chezmoi.toml.tmpl already uses promptStringOnce for email and is unaffected.