fix(date_utils): update getDayOfWeekCode to use "E" format instead of "ddd"

[FLT4613]

Description

Update format strings to match date-fns syntax after migrating from Moment.js, as the original format patterns were no longer compatible

Problem

After migrating from Moment.js to date-fns, the date format string were still using the old Moment.js syntax.

• The current "ddd" means a day of week code in moment, but the same in date-fns is not.
• It looks good to update it with 'E' as represents a day of week in date-fns

Changes

Update getDayOfWeekCode to use "E" format instead of "ddd"

Screenshots

To reviewers

Contribution checklist

• I have followed the contributing guidelines.
• I have added sufficient test coverage for my changes.
• I have formatted my code with Prettier and checked for linting issues with ESLint for code readability.