fix(launcher): relax stdout check for gRPC server startup

[germa89]

Match "GRPC SERVER" (instead of the stricter "START GRPC SERVER") when
detecting MAPDL's "Server listening on" output. This makes the startup
detection more robust to variations in MAPDL log messages.

Description

Please provide a brief description of the changes made in this pull request.

Issue linked

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Checklist

• I have visited and read Develop PyMAPDL.
• I have tested my changes locally
• I have added necessary documentation or updated existing documentation.
• I have followed the PyMAPDL coding style guidelines.
• I have added appropriate unit tests that also ensure the minimal coverage criteria.
• I have reviewed my changes before submitting this pull request.
• I have linked the issue or issues that are solved to the PR if any.
• I have assigned this PR to myself.
• I have marked this PR as draft if it is not ready to be reviewed yet.
• I have made sure that the title of my PR follows Commit naming conventions (e.g. feat: adding new MAPDL command)

[Copilot]

Pull Request Overview

This PR relaxes the stdout check for gRPC server startup detection in the MAPDL launcher to improve robustness. The change makes the startup detection less strict by matching a shorter substring of the MAPDL log output.

• Modified the gRPC server detection pattern from "START GRPC SERVER" to "GRPC SERVER"

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.18%. Comparing base (e6ca79f) to head (fddee12).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4299      +/-   ##
==========================================
- Coverage   91.29%   91.18%   -0.12%     
==========================================
  Files         193      193              
  Lines       15742    15742              
==========================================
- Hits        14372    14354      -18     
- Misses       1370     1388      +18     

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[germa89]

I need this... sooo..

@pyansys-ci-bot LGTM.

[pyansys-ci-bot]

✅ Approving this PR because germa89 said so in here 😬