patch 8.2.2601: memory usage test often fails on FreeBSD

Problem:    Memory usage test often fails on FreeBSD.
Solution:   Increase multiplier for upper limit.
diff --git a/src/testdir/test_memory_usage.vim b/src/testdir/test_memory_usage.vim
index 4f78d9a..3b7b372 100644
--- a/src/testdir/test_memory_usage.vim
+++ b/src/testdir/test_memory_usage.vim
@@ -147,9 +147,9 @@
   " The usage may be a bit less than the last value, use 80%.
   " Allow for 20% tolerance at the upper limit.  That's very permissive, but
   " otherwise the test fails sometimes.  On Cirrus CI with FreeBSD we need to
-  " be even more permissive.
+  " be even much more permissive.
   if has('bsd')
-    let multiplier = 15
+    let multiplier = 19
   else
     let multiplier = 12
   endif