Revert "Add crates for building OpenMLS"

This reverts commit f8dd9d617e0e1afe45015383e86edf8abe22993d.

Reason for revert: These were imported during prototyping, but we later decided to use the mls-rs crates instead: go/openmls-mls-rs-comparison.

Change-Id: Ibe62156c8945614024af55e67691e593cb83f5b9
diff --git a/default.xml b/default.xml
index 64b913c..d602762 100644
--- a/default.xml
+++ b/default.xml
@@ -695,8 +695,6 @@
   <project path="external/rust/crates/once_cell" name="platform/external/rust/crates/once_cell" groups="pdk" />
   <project path="external/rust/crates/oneshot-uniffi" name="platform/external/rust/crates/oneshot-uniffi" groups="pdk" />
   <project path="external/rust/crates/oorandom" name="platform/external/rust/crates/oorandom" groups="pdk" />
-  <project path="external/rust/crates/openmls" name="platform/external/rust/crates/openmls" groups="pdk" />
-  <project path="external/rust/crates/openmls_traits" name="platform/external/rust/crates/openmls_traits" groups="pdk" />
   <project path="external/rust/crates/openssl" name="platform/external/rust/crates/openssl" groups="pdk" />
   <project path="external/rust/crates/openssl-macros" name="platform/external/rust/crates/openssl-macros" groups="pdk" />
   <project path="external/rust/crates/os_str_bytes" name="platform/external/rust/crates/os_str_bytes" groups="pdk" />
@@ -798,8 +796,6 @@
   <project path="external/rust/crates/tinytemplate" name="platform/external/rust/crates/tinytemplate" groups="pdk" />
   <project path="external/rust/crates/tinyvec" name="platform/external/rust/crates/tinyvec" groups="pdk" />
   <project path="external/rust/crates/tinyvec_macros" name="platform/external/rust/crates/tinyvec_macros" groups="pdk" />
-  <project path="external/rust/crates/tls_codec" name="platform/external/rust/crates/tls_codec" groups="pdk" />
-  <project path="external/rust/crates/tls_codec_derive" name="platform/external/rust/crates/tls_codec_derive" groups="pdk" />
   <project path="external/rust/crates/tokio" name="platform/external/rust/crates/tokio" groups="pdk" />
   <project path="external/rust/crates/tokio-macros" name="platform/external/rust/crates/tokio-macros" groups="pdk" />
   <project path="external/rust/crates/tokio-stream" name="platform/external/rust/crates/tokio-stream" groups="pdk" />