Auto merge of #51121 - Manishearth:rust-syntax, r=killercup

Mark .fixed files as Rust syntax for GitHub

r? @killercup

Author: bors

.gitattributes

@@ -4,6 +4,7 @@
 *.cpp rust
 *.h rust
 *.rs rust
+*.fixed linguist-language=Rust
 src/etc/installer/gfx/* binary
 *.woff binary
 src/vendor/** -text