Docs: specify XML document name in xml.etree.elementtree example (#24… #2

Job	Run time
i686-pc-windows-msvc/msvc (Debug)	17m 57s
i686-pc-windows-msvc/msvc (Release)	22m 8s
x86_64-pc-windows-msvc/msvc (Debug)	17m 37s
x86_64-pc-windows-msvc/msvc (Release)	23m 3s
aarch64-pc-windows-msvc/msvc (Debug)	5m 35s
aarch64-pc-windows-msvc/msvc (Release)	6m 44s
x86_64-apple-darwin/clang (Debug)	9m 52s
x86_64-apple-darwin/clang (Release)	14m 6s
aarch64-apple-darwin/clang (Debug)	8m 48s
aarch64-apple-darwin/clang (Release)	13m 4s
x86_64-unknown-linux-gnu/gcc (Debug)	7m 31s
x86_64-unknown-linux-gnu/gcc (Release)	17m 37s
x86_64-unknown-linux-gnu/clang (Debug)	7m 48s
x86_64-unknown-linux-gnu/clang (Release)	15m 56s
aarch64-unknown-linux-gnu/gcc (Debug)	1h 0m 21s
aarch64-unknown-linux-gnu/gcc (Release)	48m 54s
aarch64-unknown-linux-gnu/clang (Debug)	55m 11s
aarch64-unknown-linux-gnu/clang (Release)	31m 27s
	6h 23m 39s

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