Satochip: correct flake8 issue in __init__.py

flake8 . --count --select="$ELECTRUM_LINTERS" --ignore="$ELECTRUM_LINTERS_IGNORE" --show-source --statistics --exclude "*_pb2.py,electrum/_vendor/"
./electrum/plugins/satochip/__init__.py:6:23: W292 no newline at end of file
available_for = ['qt']                      ^
1     W292 no newline at end of file

electrum/plugins/satochip/__init__.py

@@ -3,4 +3,4 @@
 description = 'Provides support for Satochip hardware wallet'
 requires = [('satochip', 'github.com/Toporin/pysatochip')]
 registers_keystore = ('hardware', 'satochip', "Satochip wallet")
-available_for = ['qt']
+available_for = ['qt']