Add PolicyType requirements for PNF Descriptor chapter

Proposed change:

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5.1.10.10. Policy Types 

Requirement: R-596064

target: PNF

keyword: MUST

introduced:  Dublin

The PNFD provided by a PNF vendor MUST comply with the following Policy Types as specified in ETSI NFV-SOL001 standard :

—tosca.datatypes.nfv.SecurityGroupRul

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