surrealdb: use default Rust toolchain and update build path (#12738)

Since the merge of #12075 reverting #11681, these lines are no longer
needed and may in fact be breaking the build.

The `lib` directory referenced for building the fuzzers was also renamed
to `sdk` in surrealdb/surrealdb#4561.

projects/surrealdb/Dockerfile

@@ -18,10 +18,6 @@ FROM gcr.io/oss-fuzz-base/base-builder-rust
 RUN git clone --depth 1 https://github.com/surrealdb/surrealdb surrealdb
 RUN git clone --depth 1 https://github.com/surrealdb/docs.surrealdb.com.git surrealdb_website
 WORKDIR surrealdb
-# TODO(gguillemas): Remove `RUN rustup.*` lines once
-# google/oss-fuzz#11681 is reverted to use nightly in image builder.
-RUN rustup install nightly
-RUN rustup default nightly
 # needed for MSAN and coverage build
 RUN rustup component add rust-src
 COPY build.sh $SRC/

projects/surrealdb/build.sh

@@ -14,7 +14,7 @@
 # limitations under the License.
 #
 ################################################################################
-cd lib
+cd sdk 
 
 # Copy dictionaries, but don't fail if there aren't any.
 cp fuzz/fuzz_targets/*.dict $OUT/ || true