Docs/grammar fix providers-singleton, issue #917 #1320

Job	Run time
Run tests with different pydantic versions	3m 25s
Run tests (3.8)	1m 53s
Run tests (3.11)	1m 55s
Run tests (3.9)	1m 51s
Run tests (3.12)	1m 52s
Run tests with coverage	2m 46s
Run linters (mypy)	1m 40s
Run tests (3.13)	2m 0s
Run tests (3.10)	1m 58s
Run linters (pydocstyle)	1m 32s
Run linters (flake8)	1m 30s
Run linters (pylint)	1m 37s
	23m 59s

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