Fix signing property check in build script (processing#1266)

Corrects the property name from 'signing.signingInMemoryKey' to 'signingInMemoryKey' in the signing condition to ensure proper detection of signing configuration.

Author: Stefterv

java/preprocessor/build.gradle.kts

@@ -50,7 +50,7 @@ mavenPublishing{
     publishToMavenCentral(SonatypeHost.CENTRAL_PORTAL)
 
     // Only sign if signing is set up
-    if(project.hasProperty("signing.keyId") || project.hasProperty("signing.signingInMemoryKey"))
+    if(project.hasProperty("signing.keyId") || project.hasProperty("signingInMemoryKey"))
         signAllPublications()
 
     pom{