MudCard: Fix content not filling remaining space

[danielchalmers]

Description

Makes the card a flex display in order to configure the content to be the one that grows in the case where the card is taller than all the children combined. This is similar to #8743

How Has This Been Tested?

visually

Type of Changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation (fix or improvement to the website or code docs)

Before

After

Checklist

• The PR is submitted to the correct branch (dev).
• My code follows the code style of this project.
• I've added relevant tests.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.48%. Comparing base (28bc599) to head (e33f0ad).
Report is 176 commits behind head on dev.

Additional details and impacted files

@@            Coverage Diff             @@
##              dev    #8933      +/-   ##
==========================================
+ Coverage   89.82%   90.48%   +0.65%     
==========================================
  Files         412      419       +7     
  Lines       11878    12189     +311     
  Branches     2364     2380      +16     
==========================================
+ Hits        10670    11029     +359     
+ Misses        681      628      -53     
- Partials      527      532       +5     

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[danielchalmers]

Looks good @henon ?

[henon]

Thanks. Even though it can be considered to be just a bugfix I still added it to the migration guide to be safe.