Update Rust crate base64 to 0.21.4 (#17)

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This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| [base64](https://togithub.com/marshallpierce/rust-base64) | dependencies | patch | `0.21.0` -> `0.21.4` |

---

### Release Notes

<details>
<summary>marshallpierce/rust-base64 (base64)</summary>

### [`v0.21.4`](https://togithub.com/marshallpierce/rust-base64/blob/HEAD/RELEASE-NOTES.md#0214)

[Compare Source](https://togithub.com/marshallpierce/rust-base64/compare/v0.21.3...v0.21.4)

-   Make `encoded_len` `const`, allowing the creation of arrays sized to encode compile-time-known data lengths

### [`v0.21.3`](https://togithub.com/marshallpierce/rust-base64/blob/HEAD/RELEASE-NOTES.md#0213)

[Compare Source](https://togithub.com/marshallpierce/rust-base64/compare/v0.21.2...v0.21.3)

-   Implement `source` instead of `cause` on Error types
-   Roll back MSRV to 1.48.0 so Debian can continue to live in a time warp
-   Slightly faster chunked encoding for short inputs
-   Decrease binary size

### [`v0.21.2`](https://togithub.com/marshallpierce/rust-base64/blob/HEAD/RELEASE-NOTES.md#0212)

[Compare Source](https://togithub.com/marshallpierce/rust-base64/compare/v0.21.1...v0.21.2)

-   Rollback MSRV to 1.57.0 -- only dev dependencies need 1.60, not the main code

### [`v0.21.1`](https://togithub.com/marshallpierce/rust-base64/blob/HEAD/RELEASE-NOTES.md#0211)

[Compare Source](https://togithub.com/marshallpierce/rust-base64/compare/v0.21.0...v0.21.1)

-   Remove the possibility of panicking during decoded length calculations
-   `DecoderReader` no longer sometimes erroneously ignores
    padding  [#&#8203;226](https://togithub.com/marshallpierce/rust-base64/issues/226)

#### Breaking changes

-   `Engine.internal_decode` return type changed
-   Update MSRV to 1.60.0

</details>

---

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Author: renovate[bot]

Cargo.lock

@@ -52,7 +52,7 @@ tracing-subscriber = { workspace = true, features = ["env-filter", "json"] }
 indoc = { workspace = true }
 indexmap = { workspace = true }
 mime_guess = "2.0.4"
-base64 = "0.21.0"
+base64 = "0.21.4"
 
 turbopack-binding = { workspace = true, features = [
   "__turbo_tasks",

packages/next-swc/crates/next-build/Cargo.toml

@@ -12,7 +12,7 @@ bench = false
 anyhow = { workspace = true }
 async-recursion = { workspace = true }
 async-trait = { workspace = true }
-base64 = "0.21.0"
+base64 = "0.21.4"
 const_format = "0.2.30"
 once_cell = { workspace = true }
 qstring = { workspace = true }