Allow deploying releases other than 2.5.1...

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Switch to OSS Sonatype

Deploying to OSS Sonatype has one major advantage over the (temporary)
solution to deploy to the ImageJ Maven repository: OSS Sonatype is
mirrored to Maven Central, and therefore does not require any extra
setup in the pom.xml to be able to use the referenced artifacts.

This reverts commit 593949bd("Deploy to the ImageJ Maven repository")
and fixes https://github.com/bobbylight/RSyntaxTextArea/issues/31.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>