Bump biweekly from 0.6.3 to 0.6.6 (#219)

Bumps [biweekly](https://github.com/mangstadt/biweekly) from 0.6.3 to 0.6.6.
- [Release notes](https://github.com/mangstadt/biweekly/releases)
- [Commits](mangstadt/biweekly@0.6.3...0.6.6)

---
updated-dependencies:
- dependency-name: net.sf.biweekly:biweekly
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

pom.xml

@@ -355,7 +355,7 @@
       <dependency>
         <groupId>net.sf.biweekly</groupId>
         <artifactId>biweekly</artifactId>
-        <version>0.6.3</version>
+        <version>0.6.6</version>
       </dependency>
 
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