Make stop_here actually stop

[impact27]

The return was not False in case of __tracebackhide__

[impact27]

Maybe this sould not print anything if self._wait_for_mainpyfile is True as it might not stop anyway. Trying __tracebackhide__ in spyder leads to:

Python 3.7.7 (default, Mar 10 2020, 15:43:33) 
Type "copyright", "credits" or "license" for more information.

IPython 7.16.1 -- An enhanced Interactive Python.

debugfile('/Users/quentinpeter/pyscripts/spyder/spyder/plugins/completion/languageserver/untitled0.py', wdir='/Users/quentinpeter/pyscripts/spyder/spyder/plugins/completion/languageserver')
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Reloaded modules: IPython.utils.tokenutil, IPython.core.payloadpage, IPython.core.completerlib, storemagic, autoreload, spyder, spyder.pil_patch
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> /Users/quentinpeter/pyscripts/spyder/spyder/plugins/completion/languageserver/untitled0.py(7)<module>()
      5 
      6 @author: quentinpeter
----> 7 """
      8 
      9 import IPython.core