bug(github_actions): Skip unreliable test

Signed-off-by: Lucas Schwiderski <lucas@lschwiderski.de>

tests/test-leak-client.lua

@@ -4,6 +4,18 @@ local awful = require("awful")
 local wibox = require("wibox")
 local gtable = require("gears.table")
 
+-- This test has been proven to perform unreliably on GitHub Actions.
+-- The additional Lua process that creates the test client will sometimes
+-- linger for an unpredictable amount of time.
+-- Stalling the step to check for clean-up increases the chance for success,
+-- but does not fix the issue.
+-- See https://github.com/awesomeWM/awesome/pull/3292.
+if os.getenv("GITHUB_ACTIONS") then
+    print("Skipping unreliable test 'test-leak-client'")
+    runner.run_steps { function() return true end }
+    return
+end
+
 -- Create a titlebar and return a table with references to its member widgets.
 local function create_titlebar(c)
     local parts = {}
@@ -88,20 +100,9 @@ local steps = {
             assert(not success, msg)
             assert(msg:find("invalid object"), msg)
 
-            -- On GitHub Actions, it can take a while for clients to be killed
-            -- properly.
-            local tries = 0
-            while (#objs > 0 and tries < 60) do
-                collectgarbage("collect")
-                os.execute("sleep 1")
-                tries = tries + 1
-            end
-
+            -- Check that it is garbage-collectable
+            collectgarbage("collect")
             assert(#objs == 0, "still clients left after garbage collect")
-            if tries > 0 then
-                print("Took approx. " .. tries .. " seconds to clean leaked client")
-            end
-
             return true
         end
     end,