tls-eio: restrict to mirage-crypto-rng-eio < 1.2.0
the error:
```
=== ERROR while compiling tls-eio.1.0.0 ======================================#
context 2.4.0~alpha1~dev | linux/x86_64 | ocaml-base-compiler.5.3.0 | file:///home/opam/opam-repository
path ~/.opam/5.3/.opam-switch/build/tls-eio.1.0.0
command ~/.opam/opam-init/hooks/sandbox.sh build dune runtest -p tls-eio -j 31
exit-code 1
env-file ~/.opam/log/tls-eio-7-d67be9.env
output-file ~/.opam/log/tls-eio-7-d67be9.out
output ###
(cd _build/default/eio/tests && ./fuzz.exe --repeat 200)
random ops: PASS
File "eio/tests/tls_eio.md", line 1, characters 0-0:
/usr/bin/git --no-pager diff --no-index --color=always -u _build/default/eio/tests/tls_eio.md _build/default/eio/tests/.mdx/tls_eio.md.corrected
diff --git a/_build/default/eio/tests/tls_eio.md b/_build/default/eio/tests/.mdx/tls_eio.md.corrected
index 0bc529e..01e78c1 100644
--- a/_build/default/eio/tests/tls_eio.md
+++ b/_build/default/eio/tests/.mdx/tls_eio.md.corrected
@@ -104,11 +104,15 @@ let serve_ssl ~config server_s callback =
test_client ~net ("127.0.0.1", "4433")
)
;;
+Line 4, characters 3-28:
+Alert deprecated: Mirage_crypto_rng_eio.run
+Use 'Mirage_crypto_rng_unix.use_default ()' instead.
+server -> start @ tcp:127.0.0.1:4433
+server -> connect
+handler accepted
+handler + GET / HTTP/1.1
+client <- GET
+client done.
+
- : unit = ()
```
```