Fix memory leak in normalize_language by using Cow instead of Box::le… #617

Job	Run time
Generate	1m 6s
Test (Linux)	1m 41s
Plugins (birch): asm, c, cpp, d, go, objc, rust, x86asm, zig	1m 59s
Plugins (acorn): css, html, javascript, json, scss, tsx, typescript, xml	1m 37s
Plugins (fern): agda, commonlisp, elixir, elm, erlang, gleam, haskell, idris, lean, ocaml, scheme	2m 23s
Clippy	56s
Documentation	48s
Plugins (cedar): clojure, groovy, java, kotlin, scala	1m 41s
Test (macOS)	2m 10s
Plugins (sage): c-sharp, elisp, fsharp, postscript, vb, vim	5m 40s
Plugins (maple): caddy, cmake, dockerfile, dot, graphql, hcl, ini, jq, kdl, meson, nginx, ninja, ...	3m 24s
Plugins (willow): asciidoc, diff, jinja2, markdown, svelte, typst, vue	1m 39s
Plugins (moss): ada, glsl, hlsl, julia, matlab, prolog, r, sparql, tlaplus, verilog, vhdl	2m 8s
Plugins (pine): capnp, dart, devicetree, rescript, starlark, swift, textproto, thrift, uiua, wit,...	2m 32s
Plugins (hazel): awk, bash, batch, fish, lua, perl, php, powershell, python, ruby, zsh	2m 45s
Publish crates.io	0s
Publish npm	0s
	32m 29s

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