Bump version from v2.5.0.beta1 to v2.5.0.beta2

In v2.5.0.beta2, there is an important change about precompile assets. When pre-compiling, rename a file is needed from /discourse/tmp to /discourse/public/plugin. According to our last infrastructure, both /discourse/tmp and /discourse/public/plugin were emptyDirs, failing at the time of pre-compiling due to the following error:

oc logs -f webapp-240-h67bw -c init-assets
--> Overwritting env variables ...
--> DONE
gem install holidays -v 8.0.0 -i /discourse/plugins/discourse-calendar/gems/2.6.5 --no-document --ignore-dependencies --no-user-install
Successfully installed holidays-8.0.0
1 gem installed
rake aborted!
Errno::EXDEV: Invalid cross-device link @ rb_file_s_rename - (/discourse/tmp/b066892f7e38f1a4f15e226d6b486fad, /discourse/public/plugins/discourse-calendar)
lib/discourse.rb:76:in `rename'
lib/discourse.rb:76:in `atomic_ln_s'
/discourse/lib/plugin/instance.rb:547:in `activate!'
lib/discourse.rb:224:in `block in activate_plugins!'
lib/discourse.rb:221:in `each'
lib/discourse.rb:221:in `activate_plugins!'
/discourse/config/application.rb:275:in `block in <class:Application>'
/discourse/lib/plugin_initialization_guard.rb:5:in `plugin_initialization_guard'
/discourse/config/application.rb:274:in `<class:Application>'
/discourse/config/application.rb:62:in `<module:Discourse>'
/discourse/config/application.rb:61:in `<top (required)>'
/discourse/Rakefile:7:in `require'
/discourse/Rakefile:7:in `<top (required)>'
/discourse/vendor/bundle/ruby/2.6.0/gems/rake-13.0.1/exe/rake:27:in `<top (required)>'
/usr/local/bin/bundle:23:in `load'
/usr/local/bin/bundle:23:in `<main>'
(See full trace by running task with --trace)

The commit involved is https://github.com/discourse/discourse/commit/83e649d08e0581a8e7c2ea3e69607e71b3912de0, and it corresponds to the method File.rename. Apparently, this is a known issue when trying to rename a file between diferent file systems (n.b.: https://stackoverflow.com/questions/43206198/what-does-the-exdev-cross-device-link-not-permitted-error-mean).