Add maven.restlet.org repository

[codelipenghui]

Motivation

Fix the build issue if no maven cache

[ERROR] Failed to execute goal on project pulsar-io-solr: Could not resolve dependencies for project org.apache.pulsar:pulsar-io-solr:jar:2.7.4-SNAPSHOT: Failed to collect dependencies at org.apache.solr:solr-core:jar:8.6.3 -> org.restlet.jee:org.restlet:jar:2.4.3: Failed to read artifact descriptor for org.restlet.jee:org.restlet:jar:2.4.3: Could not transfer artifact org.restlet.jee:org.restlet:pom:2.4.3 from/to maven-restlet (https://maven.restlet.com): Transfer failed for https://maven.restlet.com/org/restlet/jee/org.restlet/2.4.3/org.restlet-2.4.3.pom: sun.security.validator.ValidatorException: PKIX path validation failed: java.security.cert.CertPathValidatorException: validity check failed: NotAfter: Sun Dec 12 06:28:29 CST 2021 -> [Help 1]
[ERROR]
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR]
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/DependencyResolutionException
[ERROR]
[ERROR] After correcting the problems, you can resume the build with the command
[ERROR]   mvn <args> -rf :pulsar-io-solr

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