Update to Domains page

[jbatteh]

Describe the bug 🐞

The domains page at https://docs.sciml.ai/ModelingToolkit/stable/tutorials/domain_connections/#Basics should be updated. In particular., the defaults (i.e. defaults = [dm => 0]) in HydraulicPort and HydraulicFluid should be removed as they cause additional incorrect initialization equations with the current initialization in ModelingToolkit..

Expected behavior

A clear and concise description of what you expected to happen.

Minimal Reproducible Example 👇

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Error & Stacktrace ⚠️

Environment (please complete the following information):

• Output of using Pkg; Pkg.status()

 [961ee093] ModelingToolkit v9.69.0
  [16a59e39] ModelingToolkitStandardLibrary v2.19.1
  [1dea7af3] OrdinaryDiffEq v6.93.0
  [91a5bcdd] Plots v1.40.11

• Output of using Pkg; Pkg.status(; mode = PKGMODE_MANIFEST)

• Output of versioninfo()

Additional context

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