NCBC-4198: Update Snappier due to vulnerability

Motivation
==========
Vulnerabilities are bad, m'kay

Modification
============
Bump version in Directories.Packages.props

Results
=======
Tests all passing.

Change-Id: I5b45ac1b6e93386ae3da7dd0cae70993ec4613bf
Reviewed-on: https://review.couchbase.org/c/couchbase-net-client/+/244185
Reviewed-by: Emilien Bevierre <emilien.bevierre@couchbase.com>
Tested-by: Build Bot <build@couchbase.com>

Author: davidkelly

Directory.Packages.props

@@ -25,7 +25,7 @@
     <PackageVersion Include="Newtonsoft.Json" Version="13.0.4" />
     <PackageVersion Include="OpenTelemetry" Version="1.14.0" />
     <PackageVersion Include="OpenTelemetry.Api" Version="1.14.0" />
-    <PackageVersion Include="Snappier" Version="1.2.0" />
+    <PackageVersion Include="Snappier" Version="1.3.1" />
     <PackageVersion Include="System.IO.Hashing" Version="10.0.1" />
     <PackageVersion Include="System.IO.Pipelines" Version="10.0.1" />
     <PackageVersion Include="System.Linq.AsyncEnumerable" Version="10.0.5" />