Update dependency jwt to v3

Author: renovate[bot]

Gemfile.lock

@@ -96,7 +96,7 @@ GEM
     aws-eventstream (1.3.2)
     aws-sigv4 (1.11.0)
       aws-eventstream (~> 1, >= 1.0.2)
-    base64 (0.2.0)
+    base64 (0.3.0)
     bcrypt (3.1.20)
     benchmark (0.4.0)
     bigdecimal (3.1.9)
@@ -207,7 +207,7 @@ GEM
     jekyll-watch (2.2.1)
       listen (~> 3.0)
     json (2.12.2)
-    jwt (2.10.1)
+    jwt (3.1.2)
       base64
     kramdown (2.5.1)
       rexml (>= 3.3.9)