Bump System.Text.RegularExpressions in /src/HTTPlease.Formatters

Bumps System.Text.RegularExpressions from 4.3.0 to 4.3.1.

---
updated-dependencies:
- dependency-name: System.Text.RegularExpressions
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

src/HTTPlease.Formatters/HTTPlease.Formatters.csproj

@@ -19,7 +19,7 @@
     <PackageReference Include="System.Collections.Immutable" Version="1.2.0" />
     <PackageReference Include="System.Collections.Specialized" Version="4.3.0" />
     <PackageReference Include="System.Net.Http" Version="4.3.4" />
-    <PackageReference Include="System.Text.RegularExpressions" Version="4.3.0" />
+    <PackageReference Include="System.Text.RegularExpressions" Version="4.3.1" />
   </ItemGroup>
 
 </Project>