patch 8.1.0549: netbeans test depends on README.txt contents

Problem:    Netbeans test depends on README.txt contents.
Solution:   Use a generated file instead.
diff --git a/src/testdir/test_netbeans.py b/src/testdir/test_netbeans.py
index e0d291d..bdebb54 100644
--- a/src/testdir/test_netbeans.py
+++ b/src/testdir/test_netbeans.py
@@ -42,7 +42,7 @@
                 myfile.write(received)
 
             response = ''
-            if received.find('README.txt') > 0:
+            if received.find('XREADME.txt') > 0:
                 name = received.split('"')[1]
                 response = '5:putBufferNumber!33 "' + name + '"\n'
                 response += '5:setDot!1 3/19\n'