build(deps): bump base64 from 0.21.5 to 0.21.6

Bumps [base64](https://github.com/marshallpierce/rust-base64) from 0.21.5 to 0.21.6.
- [Changelog](https://github.com/marshallpierce/rust-base64/blob/master/RELEASE-NOTES.md)
- [Commits](https://github.com/marshallpierce/rust-base64/compare/v0.21.5...v0.21.6)

---
updated-dependencies:
- dependency-name: base64
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Cargo.lock

@@ -260,9 +260,9 @@ checksum = "9e1b586273c5702936fe7b7d6896644d8be71e6314cfe09d3167c95f712589e8"
 
 [[package]]
 name = "base64"
-version = "0.21.5"
+version = "0.21.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "35636a1494ede3b646cc98f74f8e62c773a38a659ebc777a2cf26b9b74171df9"
+checksum = "c79fed4cdb43e993fcdadc7e58a09fd0e3e649c4436fa11da71c9f1f3ee7feb9"
 
 [[package]]
 name = "bdk"
@@ -2866,7 +2866,7 @@ version = "3.0.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "1b8fcc794035347fb64beda2d3b462595dd2753e3f268d89c5aae77e8cf2c310"
 dependencies = [
- "base64 0.21.5",
+ "base64 0.21.6",
  "serde",
 ]
 
@@ -3401,7 +3401,7 @@ version = "0.11.23"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "37b1ae8d9ac08420c66222fb9096fc5de435c3c48542bc5336c51892cffafb41"
 dependencies = [
- "base64 0.21.5",
+ "base64 0.21.6",
  "bytes",
  "encoding_rs",
  "futures-core",
@@ -4325,7 +4325,7 @@ dependencies = [
  "async-trait",
  "atty",
  "backoff",
- "base64 0.21.5",
+ "base64 0.21.6",
  "bdk",
  "big-bytes",
  "bitcoin",