runtime: remove canBackTrace variable from TestGdbPython
runtime: remove canBackTrace variable from TestGdbPython

The canBackTrace variable is true for all of the architectures
Go supports and this is likely to remain the case as new
architectures are added.

Change-Id: I73900c018eb4b2e5c02fccd8d3e89853b2ba9d90
Reviewed-on: https://go-review.googlesource.com/22423
Reviewed-by: Cherry Zhang <d62e63aa42ce272d7b6a5055d97e942b33a34679@google.com>
Run-TryBot: Cherry Zhang <d62e63aa42ce272d7b6a5055d97e942b33a34679@google.com>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>

suncycheng/go,codestation/go,momchil-velikov/go,derekmarcotte/go,Cofyc/go,momchil-velikov/go,nawawi/go,polyverse-security/go,josharian/go,polyverse-security/go,momchil-velikov/go,derekmarcotte/go,nawawi/go,nawawi/go,CAFxX/go,derekmarcotte/go,nawawi/go,goodlang/good,nawawi/go,cloudflare/go,CAFxX/go,josharian/go,suncycheng/go,golang/go,derekmarcotte/go,vsekhar/elastic-go,cloudflare/go,CAFxX/go,akutz/go,momchil-velikov/go,goodlang/good,derekmarcotte/go,nawawi/go,CAFxX/go,josharian/go,codestation/go,golang/go,josharian/go,vsekhar/elastic-go,CAFxX/go,golang/go,vsekhar/elastic-go,derekmarcotte/go,ImJasonH/go,Cofyc/go,suncycheng/go,CAFxX/go,codestation/go,golang/go,suncycheng/go,Cofyc/go,CAFxX/go,akutz/go,christopher-henderson/Go,Cofyc/go,goodlang/good,akutz/go,goodlang/good,polyverse-security/go,vsekhar/elastic-go,ImJasonH/go,akutz/go,cloudflare/go,josharian/go,goodlang/good,nawawi/go,derekmarcotte/go,cloudflare/go,vsekhar/elastic-go,linux-on-ibm-z/go,Cofyc/go,suncycheng/go,suncycheng/go,josharian/go,linux-on-ibm-z/go,linux-on-ibm-z/go,ImJasonH/go,ImJasonH/go,Cofyc/go,polyverse-security/go,linux-on-ibm-z/go,Cofyc/go,josharian/go,vsekhar/elastic-go,akutz/go,momchil-velikov/go,cloudflare/go,linux-on-ibm-z/go,codestation/go,vsekhar/elastic-go,linux-on-ibm-z/go,golang/go,momchil-velikov/go,akutz/go,akutz/go,cloudflare/go,golang/go,golang/go,cloudflare/go,nawawi/go,codestation/go,codestation/go,polyverse-security/go,golang/go,linux-on-ibm-z/go,ImJasonH/go,polyverse-security/go,suncycheng/go,polyverse-security/go,akutz/go,ImJasonH/go,Cofyc/go,cloudflare/go,momchil-velikov/go,goodlang/good,codestation/go,suncycheng/go,goodlang/good,ImJasonH/go,CAFxX/go,linux-on-ibm-z/go,derekmarcotte/go,codestation/go,ImJasonH/go,goodlang/good,momchil-velikov/go,polyverse-security/go,vsekhar/elastic-go,josharian/go