release-version.sh: fix pom-scijava version check

We can't ask maven.scijava.org anymore, because it no longer
proxies Maven Central since the upgrade to Nexus v3.

So instead, we ask Maven Central directly, which works well.

Author: ctrueden

release-version.sh

@@ -181,13 +181,10 @@ test "$SKIP_VERSION_CHECK" || {
 }
 
 # Check that the project extends the latest version of pom-scijava.
-MAVEN_HELPER="$(cd "$(dirname "$0")" && pwd)/maven-helper.sh"
-test -f "$MAVEN_HELPER" ||
-	die "Missing helper script at '$MAVEN_HELPER'
-Do you have a full clone of https://github.com/scijava/scijava-scripts?"
 test "$SKIP_VERSION_CHECK" -o "$parentGAV" != "${parentGAV#$}" || {
 	debug "Checking pom-scijava parent version"
-	latestParentVersion=$(sh -$- "$MAVEN_HELPER" latest-version "$parentGAV")
+	psjMavenMetadata=https://repo1.maven.org/maven2/org/scijava/pom-scijava/maven-metadata.xml
+	latestParentVersion=$(curl -fsL "$psjMavenMetadata" | grep '<release>' | sed 's;.*>\([^<]*\)<.*;\1;')
 	currentParentVersion=${parentGAV##*:}
 	test "$currentParentVersion" = "$latestParentVersion" ||
 		die "Newer version of parent '$parentGAV' is available: $latestParentVersion.