Update repositories.txt

[CMB27]

No description provided.

[github-actions]

Arduino Lint has suggestions for possible improvements to https://github.com/CMB27/ModbusRTUSlave:

Linting library in ModbusRTUSlave
WARNING: Missing architectures field in library.properties. See                                                         
         https://arduino.github.io/arduino-cli/latest/library-specification/#libraryproperties-file-format (Rule LP043) 

Linter results for project: 0 ERRORS, 1 WARNINGS

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Linting sketch in ModbusRTUSlave/examples/Coil

Linter results for project: no errors or warnings

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Linting sketch in ModbusRTUSlave/examples/DiscreteInput

Linter results for project: no errors or warnings

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Linting sketch in ModbusRTUSlave/examples/HoldingRegister

Linter results for project: no errors or warnings

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Linting sketch in ModbusRTUSlave/examples/InputRegister

Linter results for project: no errors or warnings

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Linter results for projects: 0 ERRORS, 1 WARNINGS

[github-actions]

Your submission has now been accepted! Thanks for your contribution to the Arduino Library Manager index.

The library(s) will be available for installation via Library Manager within a day's time.

You can check the logs from the Library Manager indexer for your library(s) here:
http://downloads.arduino.cc/libraries/logs/github.com/CMB27/ModbusRTUSlave/