Pin test to `legacy` resolver to force desired error message #16003

Job	Run time
Updater	3m 16s
Lint	57s
ci (bundler, bundler1, 2, 0, bundler)	5s
ci (bundler, bundler1, 2, 1, bundler)	7s
ci (bundler, bundler2, 2, 0, bundler)	5s
ci (bundler, bundler2, 2, 1, bundler)	5s
ci (cargo, cargo, cargo)	5s
ci (common, common, common)	2m 4s
ci (composer, composer, 2, 0, composer)	4s
ci (composer, composer, 2, 1, composer)	6s
ci (docker, docker, docker)	7s
ci (elm, elm, elm)	4s
ci (git_submodules, git_submodules, gitsubmodule)	6s
ci (github_actions, github_actions, github-actions)	4s
ci (go_modules, go_module, 2, 0, gomod)	4s
ci (go_modules, go_module, 2, 1, gomod)	5s
ci (gradle, gradle, gradle)	4s
ci (hex, hex, 2, 0, mix)	5s
ci (hex, hex, 2, 1, mix)	4s
ci (maven, maven, maven)	6s
ci (npm_and_yarn, npm_and_yarn, 3, 0, npm)	4s
ci (npm_and_yarn, npm_and_yarn, 3, 1, npm)	6s
ci (npm_and_yarn, npm_and_yarn, 3, 2, npm)	5s
ci (nuget, nuget, nuget)	6s
ci (pub, pub, 2, 0, pub)	4s
ci (pub, pub, 2, 1, pub)	14s
ci (python, python, 2, 0, pip)	12m 47s
ci (python, python, 2, 1, pip)	6m 21s
ci (python, python_slow, 2, 0, pip)	5m 1s
ci (python, python_slow, 2, 1, pip)	6m 9s
ci (swift, swift, 2, 0, swift)	6s
ci (swift, swift, 2, 1, swift)	5s
ci (terraform, terraform, terraform)	7s
	38m 58s

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