Fix obvious link errors

[k-satoda]

Found by:

grep -o -E '\(#[^)]*\)' CppCoreGuidelines.md | sed -e 's/(#//' -e 's/)//' | sort -u >used-anchors.txt
grep -o -E 'name\s*=\s*"[^"]*"' CppCoreGuidelines.md | sed -r -e 's/name\s*=\s*//' -e 's/"//g' | sort -u >defined-anchors.txt
comm -13 defined-anchors.txt used-anchors.txt | tee undefined-anchors.txt

Some of the results are left unfixed; it seems not obvious to me how to fix them.

[AndrewPardoe]

Thanks, merged and pushed.