Fix screenshot URL for plotting in README.rst #43

Job	Run time
tests / Load tox environments	5s
tests / py39-test-psutil56 (ubuntu-latest)	48s
tests / py310-test-psutil57 (ubuntu-latest)	49s
tests / py311-test-psutil58-alldeps (ubuntu-latest)	1m 9s
tests / py312-test-psutil59 (ubuntu-latest)	1m 1s
tests / py39-test-psutil56 (macos-12)	1m 5s
tests / py310-test-psutil57 (macos-latest)	1m 3s
tests / py311-test-psutil58-alldeps (macos-latest)	53s
tests / py312-test-psutil59 (macos-latest)	44s
tests / py39-test-psutil56 (windows-latest)	2m 20s
tests / py310-test-psutil57 (windows-latest)	2m 0s
tests / py311-test-psutil58-alldeps (windows-latest)	2m 57s
tests / py312-test-psutil59 (windows-latest)	1m 43s
publish / Build source and wheel distribution	1m 29s
	18m 6s

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