add slf4j and test dep to dependencies.properties.

Author: zhumin8

gax-java/dependencies.properties

@@ -76,6 +76,7 @@ maven.com_google_http_client_google_http_client_gson=com.google.http-client:goog
 maven.org_codehaus_mojo_animal_sniffer_annotations=org.codehaus.mojo:animal-sniffer-annotations:1.24
 maven.javax_annotation_javax_annotation_api=javax.annotation:javax.annotation-api:1.3.2
 maven.org_graalvm_sdk=org.graalvm.sdk:graal-sdk:22.3.5
+maven_org_slf4j_slf4j_api=org.slf4j:slf4j-api:2.0.16
 
 # Testing maven artifacts
 maven.junit_junit=junit:junit:4.13.2
@@ -88,3 +89,5 @@ maven.net_bytebuddy_byte_buddy=net.bytebuddy:byte-buddy:1.15.10
 maven.org_objenesis_objenesis=org.objenesis:objenesis:2.6
 maven.org_junit_jupiter_junit_jupiter_api=org.junit.jupiter:junit-jupiter-api:5.11.3
 maven.org_junit_jupiter_junit_jupiter_params=org.junit.jupiter:junit-jupiter-params:5.11.3
+maven.ch_qos_logback_logback_classic=ch.qos.logback:logback-classic:1.3.14
+maven.ch_qos_logback_logback_core=ch.qos.logback:logback-core:1.3.14