Auto merge of rust-lang#134199 - RalfJung:gitmerge, r=oli-obk

Revert "Stop git from merging generated files"

This reverts rust-lang#133851. "-merge" makes git not even do merges if they are entirely conflict-free, which is not the behavior we want. We sometimes have conflict-free merges in generated files and it's much better if git can handle them automatically.

r? `@oli-obk`
Cc `@jieyouxu` `@Urgau`

.gitattributes

@@ -4,10 +4,8 @@
 *.cpp rust
 *.h rust
 *.rs rust diff=rust
-*.fixed linguist-language=Rust -merge
-*.mir linguist-language=Rust -merge
-*.stderr -merge
-*.stdout -merge
+*.fixed linguist-language=Rust
+*.mir linguist-language=Rust
 src/etc/installer/gfx/* binary
 src/vendor/** -text
 Cargo.lock linguist-generated=false