Update librsync-go to v0.8.5, circbuf to v0.1.3

Notable improvements these new versions bring:

* Optimized code path for generating deltas with blocks that are
  power-of-two-sized.
* Avoid allocating unbounded amounts of memory when the target differs
  completely from the source.
* Several bugfixes in edge cases that shall not affect balenaEngine.

Signed-off-by: Leandro Motta Barros <leandro@balena.io>
Change-type: patch

vendor.conf

@@ -195,8 +195,8 @@ github.com/willf/bitset                             559910e8471e48d76d9e5a1ba158
 github.com/urfave/cli                               c71fbcefd21552b70cd625b2c54466006e258ad7 # v1.22.1
 
 # balena deltas
-github.com/balena-os/librsync-go                    7457649327d3c2d2e7b7880ea239a03b1b28f7b4
-github.com/balena-os/circbuf                        56e73111d0b216a0157b0122dbba22a6bcaba395
+github.com/balena-os/librsync-go                    7b435f8f590637e8ba24e72f7cfc2d62f17e3848 # v0.8.5
+github.com/balena-os/circbuf                        2d080deeceffbd01dea0fcfa165dce64d2d6c9fc # v0.1.3
 
 # runc
 github.com/mrunalp/fileutils                        d7fdd64cc1cabe10bc154ee7d2318b07b7f296ef # v0.5.0