patch 9.2.0303: tests: zip plugin tests don't check for warning message properly

Problem:  zip plugin tests may match messages from previous test cases
          when checking for warning message.
Solution: Clear messages at the start of these tests (zeertzjq).

closes: #19926

Signed-off-by: zeertzjq <zeertzjq@outlook.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

src/testdir/test_plugin_zip.vim

@@ -257,6 +257,7 @@ def g:Test_zip_fname_evil_path()
   # needed for writing the zip file
   CheckExecutable zip
 
+  messages clear
   CopyZipFile("evil.zip")
   defer delete("X.zip")
   e X.zip
@@ -280,6 +281,7 @@ def g:Test_zip_fname_evil_path2()
   # needed for writing the zip file
   CheckExecutable zip
 
+  messages clear
   CopyZipFile("evil.zip")
   defer delete("X.zip")
   e X.zip
@@ -302,6 +304,7 @@ def g:Test_zip_fname_evil_path3()
   # needed for writing the zip file
   CheckExecutable zip
 
+  messages clear
   CopyZipFile("evil.zip")
   defer delete("X.zip")
   e X.zip

src/version.c

@@ -734,6 +734,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    303,
 /**/
     302,
 /**/