Bump askama from 0.14.0 to 0.15.6

Bumps [askama](https://github.com/askama-rs/askama) from 0.14.0 to 0.15.6.
- [Release notes](https://github.com/askama-rs/askama/releases)
- [Commits](askama-rs/askama@v0.14.0...v0.15.6)

---
updated-dependencies:
- dependency-name: askama
  dependency-version: 0.15.6
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

Cargo.lock

@@ -13,7 +13,7 @@ actix-files = "0.6.10"
 actix-web = { version = "4.13.0", default-features = false, features = [ "macros" ] }
 actix-web-httpauth = "0.8.2"
 arc-swap = "1.9.0"
-askama = { version = "0.14.0", default-features = false, features = [ "alloc", "derive", "std" ]}
+askama = { version = "0.15.6", default-features = false, features = [ "alloc", "derive", "std" ]}
 base64 = { version = "0.22.1", default-features = false }
 bcrypt = "0.17.1"
 config = "0.15.16"