treewide: fix 'ruff check' errors

This is mostly about unused imports.

A couple errors remain, but are fine in my book (using `l` as a variable
name, assigning a lambda to a variable).

2019/d03/ex2/ex2.py

@@ -2,7 +2,7 @@
 
 import sys
 from fractions import Fraction
-from typing import Dict, List, NamedTuple, Optional
+from typing import List, NamedTuple, Optional
 
 
 class Point(NamedTuple):

2019/d05/ex1/ex1.py

@@ -1,7 +1,5 @@
 #!/usr/bin/env python
 
-import sys
-from copy import deepcopy
 from enum import IntEnum
 from typing import List, NamedTuple
 

2019/d07/ex2/ex2.py

@@ -5,7 +5,7 @@ import sys
 from copy import deepcopy
 from dataclasses import dataclass, field
 from enum import IntEnum
-from typing import Callable, List, NamedTuple
+from typing import List, NamedTuple
 
 
 class ParameterMode(IntEnum):

2019/d09/ex1/ex1.py

@@ -1,11 +1,10 @@
 #!/usr/bin/env python
 
-import itertools
 import sys
 from copy import deepcopy
 from dataclasses import dataclass, field
 from enum import IntEnum
-from typing import Callable, List, NamedTuple
+from typing import List, NamedTuple
 
 
 class ParameterMode(IntEnum):

2019/d09/ex2/ex2.py

@@ -1,11 +1,10 @@
 #!/usr/bin/env python
 
-import itertools
 import sys
 from copy import deepcopy
 from dataclasses import dataclass, field
 from enum import IntEnum
-from typing import Callable, List, NamedTuple
+from typing import List, NamedTuple
 
 
 class ParameterMode(IntEnum):

2019/d10/ex2/ex2.py

@@ -4,7 +4,6 @@ import sys
 from cmath import phase
 from itertools import groupby
 from math import gcd, pi
-from pprint import pprint
 from typing import NamedTuple, Set, Tuple
 
 

2019/d13/ex1/ex1.py

@@ -3,7 +3,7 @@
 import sys
 from dataclasses import dataclass, field
 from enum import IntEnum
-from typing import Dict, Iterable, List, NamedTuple, Tuple, TypeVar
+from typing import Iterable, List, NamedTuple, Tuple, TypeVar
 
 
 class ParameterMode(IntEnum):

2019/d13/ex2/ex2.py

@@ -3,7 +3,7 @@
 import sys
 from dataclasses import dataclass, field
 from enum import IntEnum
-from typing import Dict, Iterable, List, NamedTuple, Tuple, TypeVar
+from typing import Iterable, List, NamedTuple, Tuple, TypeVar
 
 
 class ParameterMode(IntEnum):

2019/d16/ex2/ex2.py

@@ -2,8 +2,6 @@
 
 import sys
 from functools import reduce
-from itertools import chain, cycle
-from typing import Iterable, List
 
 
 def main() -> None:

2019/d19/ex2/ex2.py

@@ -4,7 +4,7 @@ import sys
 from copy import deepcopy
 from dataclasses import dataclass, field
 from enum import IntEnum
-from typing import Iterator, List, NamedTuple, Tuple
+from typing import List, NamedTuple
 
 
 class ParameterMode(IntEnum):