syncthing: bump to 1.9.0

syncthing: bump to 1.9.0

This release adds the advanced folder option caseSensitiveFS
(https://docs.syncthing.net/advanced/folder-caseSensitiveFS.html) to
disable the new safe handling of case insensitive filesystems.

Bugfixes:

    #1787: Case-only renames break stuff
    #5708: Properly handle upper-/lowercase-only file name collisions
    #6613: TestWatchRename test fails on FreeBSD.
    #6793: Error status should take precedence over Local Additions
    #6850: Global state incorrect when ignoring local change
    #6864: Folder incorrectly marked “Up to Date” after switching from “Receive Only” to “Send & Receive”
    #6867: Certificate error when built with Go 1.15
    #6886: chmod permission after editing .stignore via WebUI not preserved
    #6889: test failures with Go 1.15
    #6892: Syncthing 1.8.0 trying to connect via wrong network route
    #6898: tests in TestCopyRange fail on ppc64le with "inappropriate ioctl for device"
    #6908: NAT service fails to terminate during Shutdown
    #6910: Local Additions when deleting file after changing folder type from SR to RO
    #6922: Auto accepted folders not saved
    #6938: Modifying config during first scan corrupts folder state

Enhancements:

    #2739: Syncthing should be case insensitive by default
    #5579: Avoid anti-aliasing artifacts for svg device icons
    #6873: Don't fail dirs in receive-only folders that were removed elsewhere but exist locally

Signed-off-by: Paul Spooren <mail@aparcar.org>