[Lab Submission] Small tasks

[cpranav93]

Points raised:

• Link to sklearn docs: recommend "explained in the scikit-learn docs" instead of explained "here": solved in Make link text more descriptive #427
• minor syntax issue (: instead of =) causing "missing alt text" on an imaage in ep 4 link to source: solved in add missing alt-text descriptions #428
• Change "open a terminal" to statement that supports all users (Windows/Mac/Linux)