EC2: Fix unhandled error for nonexistent security groups

[viren-nadkarni]

This PR fixes an unhandled case where a non-existent security group when passed to RevokeSecurityGroupIngress and RevokeSecurityGroupEgress would raise an AttributeError.

  File "/home/viren/repo/moto-ext/moto/core/responses.py", line 270, in dispatch
    return cls()._dispatch(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/viren/repo/moto-ext/moto/core/responses.py", line 478, in _dispatch
    return self.call_action()
           ^^^^^^^^^^^^^^^^^^
  File "/home/viren/repo/moto-ext/moto/core/responses.py", line 575, in call_action
    response = method()
               ^^^^^^^^
  File "/home/viren/repo/moto-ext/moto/ec2/responses/security_groups.py", line 236, in revoke_security_group_ingress
    self.ec2_backend.revoke_security_group_ingress(**args)
  File "/home/viren/repo/moto-ext/moto/ec2/models/security_groups.py", line 824, in revoke_security_group_ingress
    group.group_id,
    ^^^^^^^^^^^^^^
AttributeError: 'NoneType' object has no attribute 'group_id'

The expected behaviour is as follows (tested against AWS)

$ aws ec2 revoke-security-group-ingress --group-name fasdf

An error occurred (InvalidGroup.NotFound) when calling the RevokeSecurityGroupIngress operation: The security group 'fasdf' does not exist in default VPC 'vpc-026b0bxxxxxx'

Supersedes #7428

[codecov]

Codecov Report

Attention: Patch coverage is 50.00000% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 94.29%. Comparing base (9aef694) to head (db3e016).
Report is 216 commits behind head on master.

Files	Patch %	Lines
moto/ec2/models/security_groups.py	50.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #7639      +/-   ##
==========================================
- Coverage   95.88%   94.29%   -1.60%     
==========================================
  Files         843     1082     +239     
  Lines       82578    92271    +9693     
==========================================
+ Hits        79178    87004    +7826     
- Misses       3400     5267    +1867     

Flag	Coverage Δ
servertests	29.41% <0.00%> (-3.11%)	⬇️
unittests	94.26% <50.00%> (-1.59%)	⬇️

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[bblommers]

LGTM - thanks @viren-nadkarni!

[github-actions]

This is now part of moto >= 5.0.7.dev3