Bump Guava to 31.1 (#1119)

diff --git a/pom.xml b/pom.xml
index e36c799..4f7fba1 100644
--- a/pom.xml
+++ b/pom.xml
@@ -89,7 +89,7 @@
       <dependency>
         <groupId>com.google.guava</groupId>
         <artifactId>guava</artifactId>
-        <version>29.0-jre</version>
+        <version>31.1-jre</version>
       </dependency>
       <dependency>
         <groupId>commons-io</groupId>