HBASE-27917 Set version to 4.0.0-alpha-1-SNAPSHOT on master (#5276)

Signed-off-by: Liangjun He <heliangjun@apache.org>

Author: Apache9

pom.xml

@@ -773,7 +773,7 @@
     </site>
   </distributionManagement>
   <properties>
-    <revision>3.0.0-beta-1-SNAPSHOT</revision>
+    <revision>4.0.0-alpha-1-SNAPSHOT</revision>
     <!-- override on command line to have generated LICENSE files include
          diagnostic info for verifying notice requirements -->
     <license.debug.print.included>false</license.debug.print.included>