revert major version number: new: 0.9

see issue #134
with
#134 (comment)
and
https://twitter.com/ryzerth/status/1771016439681466697

Signed-off-by: hayati ayguen <h_ayguen@web.de>

CMakeLists.txt

@@ -48,8 +48,8 @@ OPTION(PROVIDE_UDP_SERVER "Provide UDP server for tests" OFF)
 OPTION(WITH_RPC "RPC for non-Windows" OFF)
 
 # Set the version information here
-set(VERSION_INFO_MAJOR_VERSION 2) # increment major on api compatibility changes
-set(VERSION_INFO_MINOR_VERSION 1) # increment minor on feature-level changes
+set(VERSION_INFO_MAJOR_VERSION 0) # increment major on api compatibility changes
+set(VERSION_INFO_MINOR_VERSION 9) # increment minor on feature-level changes
 set(VERSION_INFO_PATCH_VERSION git) # increment patch for bug fixes and docs
 include(Version) # setup version info