To update SOL001 and SOL004 version in section 5.1.2 for VNF/PNF

Proposed change:

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5.1.2. References

1.ETSI GS NFV-SOL001 v2.5.1

2.TOSCA SIMPLE Profile in YAML v.1.2

3.ETSI GS NFV-SOL004 v.2.6.1 + NFVSOL(18)000746r3 

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