[RHELC-1617] Update ELS start date to match correct date

[r0x0d]

The ELS start date was set to a month early incorrectly. This patch is fixing the date for 2024-07-01 to fix it. We are also renaming it from ELS_RELEASE_DATA to ELS_START_DATE

Jira Issues:

• RHELC-1617

Checklist

• [ ] PR has been tested manually in a VM (either author or reviewer)
• [ ] Jira issue has been made public if possible
• [ ] [RHELC-] or [HMS-] is part of the PR title
• [ ] GitHub label has been added to help with Release notes
• [ ] PR title explains the change from the user's point of view
• [ ] Code and tests are documented properly
• [ ] The commits are squashed to as few commits as possible (without losing data)
• [ ] When merged: Jira issue has been updated to Release Pending if relevant

[has-bot]

/packit test --labels tier0

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[codecov[bot]]

Codecov Report

Attention: Patch coverage is 80.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 95.83%. Comparing base (9c4e6c0) to head (4b1dc81). Report is 1 commits behind head on main.

Files	Patch %	Lines
convert2rhel/actions/system_checks/els.py	80.00%	0 Missing and 1 partial :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1273 +/- ## ======================================= Coverage 95.83% 95.83% ======================================= Files 55 55 Lines 4756 4757 +1 Branches 836 836 ======================================= + Hits 4558 4559 +1 Misses 112 112 Partials 86 86 ``` | [Flag](https://app.codecov.io/gh/oamg/convert2rhel/pull/1273/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=oamg) | Coverage Δ | | |---|---|---| | [centos-linux-7](https://app.codecov.io/gh/oamg/convert2rhel/pull/1273/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=oamg) | `91.02% <80.00%> (+<0.01%)` | :arrow_up: | | [centos-linux-8](https://app.codecov.io/gh/oamg/convert2rhel/pull/1273/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=oamg) | `91.95% <80.00%> (+<0.01%)` | :arrow_up: | | [centos-linux-9](https://app.codecov.io/gh/oamg/convert2rhel/pull/1273/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=oamg) | `92.00% <80.00%> (+<0.01%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=oamg#carryforward-flags-in-the-pull-request-comment) to find out more.

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[Venefilyn]

We all discussed this at length and decided that current implementation is fine, just a few extra steps for the users