Update 00-sql-introduction.md

datacarpentries #250 contained the following comments: The lesson includes two Objectives (Select, group, add to, an analyze subsets of data, and Combine data across multiple tables) which are not covered in this lesson, and should be removed. 
These two objectoves have been removed.
(Checkout)

episodes/00-sql-introduction.md

@@ -9,8 +9,6 @@ objectives:
 - "Describe why relational databases are useful."
 - "Create and populate a database from a text file."
 - "Define SQLite data types."
-- "Select, group, add to, and analyze subsets of data."
-- "Combine data across multiple tables."
 keypoints:
 - "SQL allows us to select and group subsets of data, do math and other calculations, and combine data."
 - "A relational database is made up of tables which are related to each other by shared keys."