don't run git during the regress suite.

Index: test/irc.lua
--- test/irc.lua.orig
+++ test/irc.lua
@@ -5,8 +5,7 @@ local url = os.getenv("JOB_URL") or "???"
 local origin_job_prefix = 'https://builds.sr.ht/technomancy/job/'
 local is_origin = url:sub(1, #origin_job_prefix) == origin_job_prefix
 
-local branch = io.popen("git rev-parse --abbrev-ref HEAD"):read('*a')
-local is_main = branch == 'main'
+local is_main = false
 
 -- This may fail in future if libera chat once again blocks builds.sr.ht
 -- from connecting; it currently works after we asked them to look into it