Update docs in french (#878)
Update docs in french (#878)

1. Mention that else is optional in inline if expressions (mozilla/nunjucks@68a0703fce01fecf1bf241dc2fe4f51ee1e870d6)
2. Correct builtin filters intro text (mozilla/nunjucks@986a7a03b2a14af8e3cd9ab064772b36dd931e63)
3. Order builtin filters alphabetically (mozilla/nunjucks@c82d49a2f05e6629e936bcacafe049b5252f3aed)
4. fix duplicate section in docs near `expressions` (mozilla/nunjucks@a2b73b55c9603c3f805ec3fdb3fd9c2c4544037f)
devoidfury/nunjucks,mozilla/nunjucks,devoidfury/nunjucks,oddbird/nunjucks,mozilla/nunjucks,oddbird/nunjucks,devoidfury/nunjucks,mozilla/nunjucks,oddbird/nunjucks,oddbird/nunjucks