Build against Undertow 1.3.x in 4.3.x branch (retaining runtime compatibility Undertow 1.4)

Issue: SPR-14328

Author: jhoeller

build.gradle

@@ -76,7 +76,7 @@ configure(allprojects) { project ->
 	ext.tiles3Version        = "3.0.5"
 	ext.tomcatVersion        = "8.5.4"
 	ext.tyrusVersion         = "1.3.5"  // constrained by WebLogic 12.1.3 support
-	ext.undertowVersion      = "1.4.0.CR2"
+	ext.undertowVersion      = "1.3.23.Final"
 	ext.xmlunitVersion       = "1.6"
 	ext.xstreamVersion       = "1.4.9"