bracket-push: Removed excessive tests
bracket-push: Removed excessive tests

Removed all tests related to validate how to handle characters
that are not brackets and improved the naming of some test functions.
Related discussion: https://github.com/exercism/x-common/issues/127

orozcoadrian/xpython,outkaj/xpython,behrtam/xpython,de2Zotjes/xpython,oalbe/xpython,N-Parsons/exercism-python,pheanex/xpython,behrtam/xpython,exercism/xpython,orozcoadrian/xpython,exercism/xpython,jmluy/xpython,jmluy/xpython,N-Parsons/exercism-python,oalbe/xpython,smalley/python,outkaj/xpython,mweb/python,pheanex/xpython,exercism/python,exercism/python,rootulp/xpython,smalley/python,rootulp/xpython,de2Zotjes/xpython,mweb/python