Don't check for required attributes when spec doesn't have properties

[kddejong]

Issue #, if available:

Description of changes:

• Don't check for required attributes when spec doesn't have properties

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[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@cf589d6). Click here to learn what that means.
The diff coverage is 100%.

@@            Coverage Diff            @@
##             master    #1096   +/-   ##
=========================================
  Coverage          ?   87.72%           
=========================================
  Files             ?      134           
  Lines             ?     7950           
  Branches          ?     1955           
=========================================
  Hits              ?     6974           
  Misses            ?      578           
  Partials          ?      398

Impacted Files	Coverage Δ
src/cfnlint/rules/resources/properties/Required.py	86.73% <100%> (ø)

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[chuckmeyer]

👍