[electrs] Build fails due to `librocksdb-sys` build command about esplora

[tnull]

Now seeing:

Caused by:
  process didn't exit successfully: `/Users/ero/workspace/electrs/target/release/build/librocksdb-sys-9dfb302ce483f2f2/build-script-build` (exit status: 101)
  --- stderr
  thread 'main' panicked at /Users/ero/.cargo/registry/src/index.crates.io-6f17d22bba15001f/proc-macro2-1.0.37/src/fallback.rs:701:9:
  "enum_(unnamed_at_rocksdb/include/rocksdb/c_h_854_1)" is not a valid Ident
  stack backtrace:
     0: rust_begin_unwind
               at /rustc/cc66ad468955717ab92600c770da8c1601a4ff33/library/std/src/panicking.rs:595:5
     1: core::panicking::panic_fmt
               at /rustc/cc66ad468955717ab92600c770da8c1601a4ff33/library/core/src/panicking.rs:67:14
     2: proc_macro2::fallback::validate_ident
     3: proc_macro2::fallback::Ident::_new
     4: proc_macro2::fallback::Ident::new
     5: proc_macro2::imp::Ident::new
     6: proc_macro2::Ident::new
     7: bindgen::ir::context::BindgenContext::rust_ident_raw
     8: bindgen::ir::context::BindgenContext::rust_ident
     9: <bindgen::ir::enum_ty::Enum as bindgen::codegen::CodeGenerator>::codegen
    10: <bindgen::ir::ty::Type as bindgen::codegen::CodeGenerator>::codegen
    11: <bindgen::ir::item::Item as bindgen::codegen::CodeGenerator>::codegen
    12: <bindgen::ir::module::Module as bindgen::codegen::CodeGenerator>::codegen::{{closure}}
    13: <bindgen::ir::module::Module as bindgen::codegen::CodeGenerator>::codegen
    14: <bindgen::ir::item::Item as bindgen::codegen::CodeGenerator>::codegen
    15: bindgen::codegen::codegen::{{closure}}
    16: bindgen::ir::context::BindgenContext::gen
    17: bindgen::codegen::codegen
    18: bindgen::Bindings::generate
    19: bindgen::Builder::generate
    20: build_script_build::bindgen_rocksdb
    21: build_script_build::main
    22: core::ops::function::FnOnce::call_once
  note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

This seems to be rust-rocksdb/rust-rocksdb#713.

As it seems to have been fixed for a while, updating the rocksdb dependency might do the trick.