Snpsift tool references in the documentation

**Background**

In the original Fonda documentation, the `snpsift` tool is stated in the toolset as an annotation tool. However, Fonda code does not check the tool is specified anywhere and performs `snpsift` annotation in the `vcf_snpeff_annotation.py` file. Perhaps it was originally envisaged for the other, but it was not implemented? If not, in order not to mislead the user, we suggest removing such examples in the documentation.

**Approach**

Remove `snpsift` tool references in the Fonda documentation.

Search the Fonda documentation for `snpsift` references; the issue does not name specific documentation files. Remove the references described in the approach, then review the documentation to confirm that misleading `snpsift` examples no longer remain.

Written by the indexing model from the issue text.