Fixed about_hashes.rb to pass all tests

Learned about:
- creating hashes,
- hash literals,
- various ways to access and modify values in hashes,
- testing hash keys,
- combining hashes,
- default values when creating a new hash,
- that a block can be passed as a default value for new hash.

[#65851750]
Fixed line 75, 76
Merge pull request #6 from mkreyman/65851750_about_hashes_master

Fixed about_hashes.rb to pass all tests

[Delivers #65851750]