Update Logback version to 1.2.13

It must stay < 1.3 to work with slf4j 1.7.

Signed-off-by: rstoyanchev <[email protected]>

Author: rstoyanchev

build.gradle

@@ -34,7 +34,7 @@ subprojects {
     apply plugin: 'com.github.vlsi.gradle-extensions'
 
     ext['reactor-bom.version'] = '2020.0.39'
-    ext['logback.version'] = '1.3.14'
+    ext['logback.version'] = '1.2.13'
     ext['netty-bom.version'] = '4.1.106.Final'
     ext['netty-boringssl.version'] = '2.0.62.Final'
     ext['hdrhistogram.version'] = '2.1.12'