Unset reproducibleFileOrder and preserveFileTimestamps Gradle flags

This commit reverts the changes done via 50a0094
in order to ensure consistency across modules (those changes were specific to
spring-core).

Reproducible builds are likely desirable, but it is a complex topic
(see gradle/gradle#14819) that needs to be addressed portfolio wide, with
a better control than what Gradle currently allows (for example to allow
using EPOCH instead of the current 1980 date).

Basic tests did not show an obvious impact on testing avoidance with modern
Gradle versions.

Closes gh-29633

Author: sdeleuze

spring-core/spring-core.gradle

@@ -97,8 +97,6 @@ dependencies {
 }
 
 jar {
-	reproducibleFileOrder = true
-	preserveFileTimestamps = false  // maybe not necessary here, but good for reproducibility
 	manifest.attributes["Dependencies"] = "jdk.unsupported"  // for WildFly (-> Objenesis 3.2)
 
 	dependsOn javapoetRepackJar