chore: delete unused backend config in workspace

[healthjyk]

What type of PR is this?

What this PR does / why we need it:

Which issue(s) this PR fixes:

Fixes #

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[coveralls]

Pull Request Test Coverage Report for Build 8277776857

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 13 unchanged lines in 5 files lost coverage.
• Overall coverage increased (+0.4%) to 72.84%

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Files with Coverage Reduction	New Missed Lines	%
pkg/engine/operation/watch.go	1	85.93%
pkg/workspace/util.go	1	79.82%
pkg/workspace/validation.go	1	83.52%
pkg/engine/operation/parser/spec_parser.go	4	56.1%
pkg/engine/operation/parser/parser.go	6	75.61%

Totals
Change from base Build 8275253521:	0.4%
Covered Lines:	7209
Relevant Lines:	9897

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💛 - Coveralls

[adohe]

/lgtm