wscript: drop unused imports, manual

Manual fix of pyflake warnings:
libs/ardour/wscript:3:1 'waflib.Tools' imported but unused
wscript:9:1 'waflib.Build.Context' imported but unused

libs/ardour/wscript

@@ -1,6 +1,6 @@
 #!/usr/bin/env python
 from waflib.extras import autowaf as autowaf
-from waflib import Options, Task, Tools
+from waflib import Options, Task
 import os
 import re
 

wscript

@@ -6,7 +6,6 @@ import re
 import subprocess
 import sys
 import platform as PLATFORM
-from waflib.Build import Context
 from waflib.Build import BuildContext
 import waflib.Utils as Utils