MINOR: [C#] Bump System.Memory from 4.5.4 to 4.5.5 in /csharp (#43755)

Bumps System.Memory from 4.5.4 to 4.5.5.

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Authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Signed-off-by: Curt Hagenlocher <[email protected]>

csharp/src/Apache.Arrow.Flight/Apache.Arrow.Flight.csproj

@@ -8,6 +8,7 @@
     <PackageReference Include="Google.Protobuf" Version="3.27.3" />
     <PackageReference Include="Grpc.Net.Client" Version="2.65.0" />
     <PackageReference Include="Grpc.Tools" Version="2.65.0" PrivateAssets="All" />
+    <PackageReference Include="System.Memory" Version="4.5.5" />
   </ItemGroup>
 
   <ItemGroup Condition="'$(TargetFramework)'=='netstandard2.0'">