Bump commons-compress from 1.20 to 1.21 in /opengrok-indexer

Bumps commons-compress from 1.20 to 1.21.

---
updated-dependencies:
- dependency-name: org.apache.commons:commons-compress
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

opengrok-indexer/pom.xml

@@ -55,7 +55,7 @@ Portions Copyright (c) 2020-2020, Lubos Kosco <[email protected]>.
         <dependency>
             <groupId>org.apache.commons</groupId>
             <artifactId>commons-compress</artifactId>
-            <version>1.20</version>
+            <version>1.21</version>
         </dependency>
         <dependency>
             <groupId>org.apache.lucene</groupId>