go.mod: revert tailscale/breakglass fork require

Revert the direct fork dependency and its regenerated depaware/flake
manifests; not ready to ship yet.

This reverts commit 745bb8507.

Updates #1866

Signed-off-by: Kristoffer Dalby <kristoffer@tailscale.com>

cmd/tailscaled/depaware.txt

@@ -181,8 +181,7 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
    L    github.com/pierrec/lz4/v4/internal/xxh32                     from github.com/pierrec/lz4/v4/internal/lz4stream
         github.com/pires/go-proxyproto                               from tailscale.com/ipn/ipnlocal
   LD    github.com/pkg/sftp                                          from tailscale.com/ssh/tailssh
-  LD    github.com/pkg/sftp/internal/encoding/ssh/filexfer           from github.com/pkg/sftp+
-  LD    github.com/pkg/sftp/internal/encoding/ssh/filexfer/openssh   from github.com/pkg/sftp
+  LD    github.com/pkg/sftp/internal/encoding/ssh/filexfer           from github.com/pkg/sftp
    L 💣 github.com/safchain/ethtool                                  from tailscale.com/net/netkernelconf+
   DW 💣 github.com/tailscale/certstore                               from tailscale.com/control/controlclient
   LD    github.com/tailscale/gliderssh                               from tailscale.com/ssh/tailssh