remove ref epoch from episode 1 solution

[abostroem]

What is the problem?

In the solution to the exercises:
The clauses in a query have to be in the right order. Go back and change the order of the clauses in query2 and run it again. The modified query should fail, but notice that you don’t get much useful debugging information.

[Read about SQL operators here](https://www.w3schools.com/sql/sql_operators.asp) and then modify the previous query to select rows where bp_rp is between -0.75 and 2

the columns used do no match the previous query. ref_epoch should be removed and pmra and pmdec added.

Location of problem (optional)

https://datacarpentry.github.io/astronomy-python/instructor/01-query.html

[ShebMichel]

@abostroem have corrected the issue, if you can approve the pull request and once happy close this issue. Thanks