Upgrade Maven version to 3.5.4 for AppVeyor as well

Author: HyukjinKwon

dev/appveyor-install-dependencies.ps1

@@ -81,7 +81,7 @@ if (!(Test-Path $tools)) {
 # ========================== Maven
 Push-Location $tools
 
-$mavenVer = "3.3.9"
+$mavenVer = "3.5.4"
 Start-FileDownload "https://archive.apache.org/dist/maven/maven-3/$mavenVer/binaries/apache-maven-$mavenVer-bin.zip" "maven.zip"
 
 # extract