Bump serde from 1.0.98 to 1.0.99 (#5540)

Bumps [serde](https://github.com/serde-rs/serde) from 1.0.98 to 1.0.99.
- [Release notes](https://github.com/serde-rs/serde/releases)
- [Commits](https://github.com/serde-rs/serde/compare/v1.0.98...v1.0.99)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

drone/Cargo.toml

@@ -18,7 +18,7 @@ byteorder = "1.3.2"
 bytes = "0.4"
 clap = "2.33"
 log = "0.4.8"
-serde = "1.0.98"
+serde = "1.0.99"
 serde_derive = "1.0.98"
 solana-logger = { path = "../logger", version = "0.18.0-pre1" }
 solana-metrics = { path = "../metrics", version = "0.18.0-pre1" }