Fix grammar error in --help for --py-args

[btzy]

This is a minor grammar fix in the message that appears when one runs qgis --help.

The help string for --py-args used to say the following:

This arguments will be available for each python execution via 'sys.argv' included the file specified by '--code'. All arguments till '--' are passed to python and ignored by QGIS

Apart from being grammatically incorrect, it may be interpreted as saying that sys.argv is included by the file specified in --code, which was what I originally thought it meant. Instead, we actually want it to mean that the arguments will be available in all Python code that is entered, including the file specified by --code.

I also changed this to these, which is the correct form of the word to use.

[github-actions]

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