go.toolchain.rev: update to Go 1.25.5 (#18123)

Updates #18122

Signed-off-by: Brendan Creane <[email protected]>

gokrazy/natlabapp/builddir/tailscale.com/go.mod

@@ -1,6 +1,6 @@
 module gokrazy/build/tsapp
 
-go 1.23.1
+go 1.25.5
 
 replace tailscale.com => ../../../..
 

gokrazy/tsapp/builddir/tailscale.com/go.mod

@@ -1,6 +1,6 @@
 module gokrazy/build/tsapp
 
-go 1.23.1
+go 1.25.5
 
 replace tailscale.com => ../../../..