Remove 'putty -cleanup-during-uninstall' from legacy uninstaller.

It's a bit conceptually incoherent anyway - if you're uninstalling
PuTTY _systemwide_ across a multi-user system, it doesn't really make
sense that you'd also want to wipe the saved sessions for the
individual user running the uninstaller.

Also, making this change to the Inno Setup uninstaller opens up a
nicer migration path to MSI for people doing large corporate rollouts:
they can upgrade to this version of the Inno Setup package, then do a
silent uninstall of it (which should now _actually_ be silent, since
this cleanup step was the thing that interrupted it otherwise) and
then a silent install of the MSI.

windows/putty.iss

@@ -87,13 +87,6 @@ Root: HKCR; Subkey: "PuTTYPrivateKey\shell\edit"; ValueType: string; ValueName:
 Root: HKCR; Subkey: "PuTTYPrivateKey\shell\edit\command"; ValueType: string; ValueName: ""; ValueData: """{app}\puttygen.exe"" ""%1"""; Tasks: associate
 ; Add to PATH on NT-class OS?
 
-[UninstallRun]
-; -cleanup-during-uninstall is an undocumented option that tailors the
-; message displayed.
-; XXX: it would be nice if this task weren't run if a silent uninstall is
-;      requested, but "skipifsilent" is disallowed.
-Filename: "{app}\putty.exe"; Parameters: "-cleanup-during-uninstall"; RunOnceId: "PuTTYCleanup"; StatusMsg: "Cleaning up saved sessions etc (optional)..."
-
 [Messages]
 ; Since it's possible for the user to be asked to restart their computer,
 ; we should override the default messages to explain exactly why, so they