Fix build reproducibility by skipping Maven version in manifest

[lucasvuotto]

No description provided.

[lucasvuotto]

The justification for this can be found in https://maven.apache.org/shared/maven-archiver/examples/manifest.html . The default does output the current Maven version, which ended up producing differences in the built JARs here and via https://github.com/rsksmart/reproducible-builds methodology. The only difference between both JARs was

diff -ru docker/META-INF/MANIFEST.MF gha/META-INF/MANIFEST.MF
--- docker/META-INF/MANIFEST.MF 1980-01-01 12:01:00
+++ gha/META-INF/MANIFEST.MF    1980-01-01 12:01:00
@@ -1,5 +1,5 @@
 Manifest-Version: 1.0
 Archiver-Version: Plexus Archiver
-Created-By: Apache Maven 3.6.3
+Created-By: Apache Maven 3.9.11
 Build-Jdk: 1.8.0_412

By not adding the default manifest, we skip both Build-Jdk: and Created-By: fields, of which the latter can introduce meaningless differences.