Add missing thumbnail for TermSet tutorial #2345

Job	Run time
linux-gallery-python3.12-upgraded	58s
linux-gallery-python3.8-minimum	53s
windows-gallery-python3.12-upgraded	1m 45s
windows-gallery-python3.8-minimum	1m 34s
linux-python3.12-ros3	1m 12s
linux-python3.12	2m 17s
linux-python3.12-upgraded	2m 7s
linux-python3.8-minimum	1m 54s
macos-python3.12-upgraded	1m 16s
macos-python3.8-minimum	3m 0s
windows-python3.12-upgraded	3m 11s
windows-python3.8-minimum	3m 11s
conda-linux-python3.12-upgraded	2m 18s
conda-linux-python3.8-minimum	2m 26s
Deploy pre-release from dev	0s
	28m 2s

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