fix: cherry-pick acts cxxstd and newer versions

assigned to @wdconinc

enabled an automatic merge when the pipeline for c2e87aa0 succeeds

aborted the automatic merge because source branch was updated

added 1 commit

• c69b0373 - fix: actsvg: add v0.4.33

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added 1 commit

• 6b23a61a - fix: cherry-pick mlpack

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added 1 commit

• 4bdc8067 - fix: cherry-pick (r-rcpp)ensmallen

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enabled an automatic merge when the pipeline for 4bdc8067 succeeds

merged