defaults.env: quote GIT_USER_NAME to avoid error when sourcing .env

Since this commit:
df646b6 Issue #396: Use arm64v8 images for services
.env is sourced and it fails "Doe: command not found"

Without the quotes, it would also fail with a valid name filled.

env/defaults.env

@@ -4,7 +4,7 @@ EDITOR=vim
 GIT_BZ_PASSWORD=nothing
 GIT_BZ_USER=you@example.com
 GIT_USER_EMAIL=you@example.com
-GIT_USER_NAME=John Doe
+GIT_USER_NAME="John Doe"
 DEBUG_GIT_REPO_MISC4DEV=no
 DEBUG_GIT_REPO_MISC4DEV_URL=https://gitlab.com/koha-community/koha-misc4dev.git
 DEBUG_GIT_REPO_MISC4DEV_BRANCH=master
@@ -43,4 +43,4 @@ CPAN=no
 INSTALL_MISSING_FROM_CPANFILE=no
 KEYCLOAK_ADMIN=keycloak
 KEYCLOAK_ADMIN_PASS=keycloak
-KEYCLOAK_REALM=koha
+KEYCLOAK_REALM=koha