Fix bug : meal labels date not changing

[lamontfr]

Fixes #820

Changes proposed in this pull request:

• src/delivery/views.py : meals labels date was static by mistake

  Status

• [X] READY

  How to verify this change

• access the Kitchen count from the left side tabs
• make sure there is at least one order for today (if not generate them or create one manually)
• click on Step 2 "Ingredients"
• Select a recipe to load the ingredients and pick a random side dish ingredient
• Click confirm all ingredients
• Click "Next: Print kitchen count"
• Click on the pink "Labels" button
• Open the PDF and verify that the date is equal to today's date

[coveralls]

Coverage increased (+0.01%) to 95.278% when pulling d62378d414adf79e27f4e74e2a6f7b87b0f9e9b9 on lamontfr:fix820 into 844ca09186124734e6db774d3e832801fde2b613 on savoirfairelinux:dev.