Update supported WP version to 6.3

[m1r0]

Proposed Changes

This PR updates the supported WP version to 6.3 and the minimum required version to 6.1.

Testing Instructions

1. Install WP 6.3.
2. Make sure the plugin is working.

Pre-Merge Checklist

• PR title and description contain sufficient detail and accurately describe the changes
• Acceptance criteria is met
• Decisions are publicly documented
• Adheres to coding standards (PHP, JavaScript, CSS, HTML)
• All strings are translatable (without concatenation, handles plurals)
• Follows our naming conventions (P6rkRX-4oA-p2)
• Hooks (p6rkRX-1uS-p2) and functions are documented
• New UIs are responsive and use a mobile-first approach
• New UIs match the designs
• Different user privileges (admin, teacher, subscriber) are tested as appropriate
• Code is tested on the minimum supported PHP and WordPress versions
• User interface changes have been tested on the latest versions of Chrome, Firefox and Safari
• "Needs Documentation" label is added if this change requires updates to documentation
• Known issues are created as new GitHub issues

[codecov]

Codecov Report

Merging #7057 (f979ba1) into trunk (c1a9bb1) will not change coverage.
Report is 29 commits behind head on trunk.
The diff coverage is 79.94%.

@@            Coverage Diff            @@
##              trunk    #7057   +/-   ##
=========================================
  Coverage     49.32%   49.32%           
  Complexity    10538    10538           
=========================================
  Files           575      575           
  Lines         44501    44501           
  Branches        402      402           
=========================================
  Hits          21950    21950           
  Misses        22224    22224           
  Partials        327      327           

Files Changed	Coverage Δ
includes/class-sensei.php	23.41% <0.00%> (ø)
...al/student-progress/tools/class-migration-tool.php	31.03% <31.03%> (ø)
...er/migrations/class-student-progress-migration.php	80.89% <80.89%> (ø)
...ncludes/blocks/class-sensei-block-view-results.php	74.28% <100.00%> (ø)
includes/class-sensei-settings-api.php	15.47% <100.00%> (ø)
includes/class-sensei-settings.php	70.70% <100.00%> (ø)
includes/internal/emails/class-email-sender.php	99.02% <100.00%> (ø)
...ludes/internal/emails/class-email-settings-tab.php	85.82% <100.00%> (ø)

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