Post Variant Calling Metric "SVN count" ID should probly by `pass_snv_count`

[c-BIG-admin]

To be more aligned with Post Alignment Metric IDs, it might be better to name (ie metric's ID) it pass_snv_count

https://github.com/ga4gh/quality-control-wgs/blob/d32d9272da2341cb6031af64167e74e2f88f7f37/metrics_definitions/metrics_definitions.md?plain=1#L99

@justinjj24, What do you think ?

[justinjj24]

Agree. Updated the metric definiton ID as follows..

• Count: SNVs - ID: count_snvs_pass
• Count: Insertions - ID: count_insertions_pass
• Count: Deletions - ID: count_deletions_pass
• Ratio: Insertions/Deletions - ID: ratio_insertion_deletion_pass
• Ratio: Heterozygous/Homozygous (SNVs) - ID: ratio_heterozygous_homzygous_snv_pass
• Ratio: Heterozygous/Homozygous (indels) - ID: ratio_heterozygous_homzygous_indel_pass
• Ratio: Transitions/Transversions (ti/tv) - ID: ratio_transitions_transversions_pass