relnotes: copy contents of "next" to "5.8" and clear "next"
The same procedure as every year^Wcycle.
Unlike previous cycles, I haven't actually recorded the copy because
we don't want to propagate further changes in "next" (from the stable
branch) to "5.8".
Differential Revision: https://phab.mercurial-scm.org/D10500
{
"version": 1,
"project": "mercurial",
"project_url": "https://mercurial-scm.org/",
"repo": "..",
"branches": ["default", "stable"],
"environment_type": "virtualenv",
"show_commit_url": "https://www.mercurial-scm.org/repo/hg/rev/",
"benchmark_dir": "benchmarks",
"env_dir": "../.asv/env",
"results_dir": "../.asv/results",
"html_dir": "../.asv/html"
}