Remove redundant symbolic alt to so term hash

[nakib103]

Reported in Ensembl/VEP_plugins#710
Also see Ensembl/ensembl-variation#1075

[nakib103]

@nuno-agostinho,
The unit test on one before the last take accounts the change in ensembl-variation and passed. You can ignore the unit test failure in the last commit.

[nuno-agostinho]

Same concern as expressed in Ensembl/ensembl-variation#1075 (review).

Otherwise, I just have small suggestions.

[nuno-agostinho]

No need to export _valid_region_regex, it was only being used within check_format for ensembl-variation (confirm?)

[nakib103]

it is used in -

• ensembl-vep/modules/Bio/EnsEMBL/VEP/Parser/Region.pm

  Line 171 in 31a3581

  return [] unless $region =~ &_valid_region_regex();

  which is a child class so no need of import.
• check_format for ensembl-variation. We need to import for that. I am just giving preference to remove redundancy.