Kill table geneToTerm

[fbastian]

The table geneToTerm is not currently used anywhere (I think it was used in bgee 12).

In the new script made by Patrick to insert species not in Ensembl, this table is not filled. I think it's important to keep everything consistent. Since we don't currently use this table, I think it's better to simply kill it (so that we don't forget one day that species not in Ensembl have no information in this table)

• Modify script insert_genes.pl
• Modify database schema