Update askama requirement from 0.7.2 to 0.9.0 (#2187)

Updates the requirements on [askama](https://github.com/djc/askama) to permit the latest version.
- [Release notes](https://github.com/djc/askama/releases)
- [Commits](https://github.com/djc/askama/compare/0.7.2...0.9.0)

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

Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>

examples/todomvc/Cargo.toml

@@ -8,12 +8,12 @@ edition = "2018"
 crate-type = ["cdylib"]
 
 [build-dependencies]
-askama = "0.7.2"
+askama = "0.9.0"
 
 [dependencies]
 js-sys = "0.3.40"
 wasm-bindgen = "0.2.63"
-askama = "0.7.2"
+askama = "0.9.0"
 console_error_panic_hook = "0.1.5"
 
 [dependencies.web-sys]