Update Bindgen dependency

[bvaisvil]

This PR updates bindgen to 0.69.4. There is a security issue in shlex version 1.1.0 which is a dependency of bindgen this PR fixes that issue.

Additionally, the newer version of bindgen deprecated the use of the constant bindgen::CargoCallbacks. So that is replaced as recommended with CargoCallbacks::new().

Code passed all tests, but with 43 warnings of dereferencing a null pointer, which remains unchanged from the master branch.

running 24 tests
test c_headers::bindgen_test_layout___kernel_fd_set ... ok
test c_headers::bindgen_test_layout___kernel_fsid_t ... ok
test c_headers::bindgen_test_layout___kernel_sockaddr_storage ... ok
test c_headers::bindgen_test_layout_genlmsghdr ... ok
test c_headers::bindgen_test_layout_nl_mmap_hdr ... ok
test c_headers::bindgen_test_layout_nl_mmap_req ... ok
test c_headers::bindgen_test_layout_nl_pktinfo ... ok
test c_headers::bindgen_test_layout_nlattr ... ok
test c_headers::bindgen_test_layout_nla_bitfield32 ... ok
test c_headers::bindgen_test_layout_nlmsgerr ... ok
test c_headers::bindgen_test_layout_nlmsghdr ... ok
test c_headers::bindgen_test_layout_sockaddr_nl ... ok
test c_headers::bindgen_test_layout_sysinfo ... ok
test c_headers::bindgen_test_layout_taskstats ... ok
test netlink::tests::test_gennlmsg_payload ... ok
test format::tests::test_print_full ... ok
test netlink::tests::test_nlattr_payload ... ok
test netlink::tests::test_nlpayload ... ok
test format::tests::test_print_delay_lines ... ok
test format::tests::test_print_summary_lines ... ok
test netlink::tests::test_nlpayload_nlattrs ... ok
test tests::test_struct_taskstats_alignment ... ok
test netlink::tests::test_send_cmd ... ok
test netlink::tests::test_recv_response ... ok

test result: ok. 24 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s

     Running unittests src/bin/taskstats/main.rs (target/debug/deps/taskstats-dae3fa9258528d3d)

running 0 tests

test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s

   Doc-tests linux-taskstats

running 0 tests

test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s

[kawamuray]

LGTM, thanks!