Update tree-sitter-diff (helix-editor#3708)

This change also renames the grammar from `git-diff` to `diff`.
The grammar covers regular diff syntax so I renamed the repository
a while ago.

book/src/generated/lang-support.md

@@ -15,6 +15,7 @@
 | cue | ✓ |  |  | `cuelsp` |
 | dart | ✓ |  | ✓ | `dart` |
 | devicetree | ✓ |  |  |  |
+| diff | ✓ |  |  |  |
 | dockerfile | ✓ |  |  | `docker-langserver` |
 | dot | ✓ |  |  | `dot-language-server` |
 | edoc | ✓ |  |  |  |
@@ -32,7 +33,6 @@
 | git-attributes | ✓ |  |  |  |
 | git-commit | ✓ |  |  |  |
 | git-config | ✓ |  |  |  |
-| git-diff | ✓ |  |  |  |
 | git-ignore | ✓ |  |  |  |
 | git-rebase | ✓ |  |  |  |
 | gleam | ✓ | ✓ |  | `gleam` |

languages.toml

@@ -978,7 +978,7 @@ name = "git-commit"
 source = { git = "https://github.com/the-mikedavis/tree-sitter-git-commit", rev = "318dd72abfaa7b8044c1d1fbeabcd06deaaf038f" }
 
 [[language]]
-name = "git-diff"
+name = "diff"
 scope = "source.diff"
 roots = []
 file-types = ["diff"]
@@ -987,8 +987,8 @@ comment-token = "#"
 indent = { tab-width = 2, unit = "  " }
 
 [[grammar]]
-name = "git-diff"
-source = { git = "https://github.com/the-mikedavis/tree-sitter-git-diff", rev = "c12e6ecb54485f764250556ffd7ccb18f8e2942b" }
+name = "diff"
+source = { git = "https://github.com/the-mikedavis/tree-sitter-diff", rev = "fd74c78fa88a20085dbc7bbeaba066f4d1692b63" }
 
 [[language]]
 name = "git-rebase"