fix linting errors

Author: Iván García Sainz-Aja

provider/pact-jvm-provider-maven/src/main/kotlin/au/com/dius/pact/provider/maven/PactPublishMojo.kt

@@ -13,7 +13,7 @@ import java.io.File
 @Mojo(name = "publish")
 open class PactPublishMojo : PactBaseMojo() {
 
-    @Parameter(defaultValue = "false", expression="${skipPactPublish}")
+    @Parameter(defaultValue = "false", expression = "\${skipPactPublish}")
     private var skipPactPublish: Boolean = false
 
     @Parameter(required = true, defaultValue = "\${project.version}")