patch 8.2.3253: channel test fails randomly

Problem:    Channel test fails randomly.
Solution:   Add a sleep after sending the "echoerr" command. (Michael Soyka)
diff --git a/src/testdir/test_channel.py b/src/testdir/test_channel.py
index 9684bb9..36aad2b 100644
--- a/src/testdir/test_channel.py
+++ b/src/testdir/test_channel.py
@@ -114,6 +114,11 @@
                         print("sending: {0}".format(cmd))
                         self.request.sendall(cmd.encode('utf-8'))
                         response = "ok"
+                        # Wait a bit, so that the "ex" command is handled
+                        # before the "ch_evalexpr() returns.  Otherwise we are
+                        # outside the try/catch when the "ex" command is
+                        # handled.
+                        time.sleep(0.02)
                     elif decoded[1] == 'bad command':
                         cmd = '["ex","foo bar"]'
                         print("sending: {0}".format(cmd))
diff --git a/src/testdir/test_channel.vim b/src/testdir/test_channel.vim
index f2c0d17..fc82ada 100644
--- a/src/testdir/test_channel.vim
+++ b/src/testdir/test_channel.vim
@@ -253,11 +253,6 @@
 func Test_communicate_ipv6()
   CheckIPv6
 
-  " FIXME: this test is very flaky on MS-Windows
-  if has('win32')
-    throw 'Skipped: test is very flaky with MS-Windows'
-  endif
-
   call Test_communicate()
 endfunc