Bump version to v2.12.0 (#5003)

Author: vicentebolea

ReadMe.md

@@ -52,7 +52,7 @@ If you find ADIOS2 useful, please cite our [SoftwareX paper](https://doi.org/10.
 
 ## Releases
 
-* Latest release: [v2.12.0-rc1](https://github.com/ornladios/ADIOS2/releases/tag/v2.12.0-rc1)
+* Latest release: [v2.12.0](https://github.com/ornladios/ADIOS2/releases/tag/v2.12.0)
 * Previous releases: [https://github.com/ornladios/ADIOS2/releases](https://github.com/ornladios/ADIOS2/releases)
 
 ## Packages

docs/user_guide/source/conf.py

@@ -70,7 +70,7 @@
 # The short X.Y version.
 version = "2"
 # The full version, including alpha/beta/rc tags.
-release = "2.12.0-rc1"
+release = "2.12.0"
 
 # The language for content autogenerated by Sphinx. Refer to documentation
 # for a list of supported languages.