Replace the 'z' directives in sd.skool with 's' directives

The 'z' directive is deprecated in SkoolKit 3.7.
Replace the 'z' directives in bts.skool with 's' directives

The 'z' directive is deprecated in SkoolKit 3.7.
Replace the 'z' directives in csc.skool with 's' directives

The 'z' directive is deprecated in SkoolKit 3.7.