Bump bootsnap from 1.19.0 to 1.20.1 in /demo (#3839)

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

Author: dependabot[bot]

demo/Gemfile.lock

@@ -54,7 +54,7 @@ GEM
     base64 (0.3.0)
     benchmark (0.5.0)
     bigdecimal (4.0.1)
-    bootsnap (1.19.0)
+    bootsnap (1.21.0)
       msgpack (~> 1.2)
     builder (3.3.0)
     byebug (12.0.0)