Tutorial: Fix variable name typo in step 1
There's a reference to CMAKE_CXX_REQUIRED_STANDARD in a comment in tutorial step 1, but I think it's meant to be CMAKE_CXX_STANDARD_REQUIRED.
Backport: release
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There's a reference to CMAKE_CXX_REQUIRED_STANDARD in a comment in tutorial step 1, but I think it's meant to be CMAKE_CXX_STANDARD_REQUIRED.
Backport: release