Remove com.google.code.findbugs:jsr305 dependency and use org.jetbrains.annotations.Nullable (#920)

Closes #912

Author: dbyron0

core/build.gradle

@@ -76,7 +76,6 @@ dependencies {
     compile 'org.slf4j:slf4j-ext:1.7.25'
     compile 'org.jetbrains:annotations:15.0'
     compile 'javax.annotation:javax.annotation-api:1.3.1'
-    compile 'com.google.code.findbugs:jsr305:3.0.2'
     compile 'org.apache.commons:commons-compress:1.18'
     // Added for JDK9 compatibility since it's missing this package
     compile 'javax.xml.bind:jaxb-api:2.3.0'

core/src/main/java/org/testcontainers/dockerclient/transport/okhttp/OkHttpInvocationBuilder.java

@@ -31,9 +31,9 @@
 import okio.BufferedSource;
 import okio.Okio;
 import okio.Source;
+import org.jetbrains.annotations.Nullable;
 import org.testcontainers.DockerClientFactory;
 
-import javax.annotation.Nullable;
 import java.io.ByteArrayInputStream;
 import java.io.IOException;
 import java.io.InputStream;