don't uppercase error messages

a more general version of https://github.com/rust-lang/rust/pull/146080.

after a bit of hacking in [`fluent.rs`](https://github.com/rust-lang/rust/blob/master/compiler/rustc_fluent_macro/src/fluent.rs), i discovered that i'm not the only one that is bad at following guidelines :sweat_smile:. this pr lowercases the first letter of all the error messages in the codebase.

(i did not change things that are traditionally uppercased such as _MIR_, _ABI_ or _C_)

i think it's reasonable to run a `@bors try` so all the test suite is checked, as i cannot run some of the tests on my machine. i double checked (and replaced manually) all the old error messages, but better be safe than sorry.

in the future i will try to add a check in `x test tidy` that errors if an error message starts with an uppercase letter.

1 files changed, 1 insertions, 1 deletions

diff --git a/tests/ui/pattern/at-in-struct-patterns.rs b/tests/ui/pattern/at-in-struct-patterns.rs
index e8fad61f317..b0557220d05 100644
--- a/tests/ui/pattern/at-in-struct-patterns.rs
+++ b/tests/ui/pattern/at-in-struct-patterns.rs
@@ -5,7 +5,7 @@ struct Foo {
 
 fn main() {
     let foo = Foo { field1: 1, field2: 2 };
-    let Foo { var @ field1, .. } = foo; //~ ERROR Unexpected `@` in struct pattern
+    let Foo { var @ field1, .. } = foo; //~ ERROR unexpected `@` in struct pattern
     dbg!(var); //~ ERROR cannot find value `var` in this scope
     let Foo { field1: _, bar @ .. } = foo; //~ ERROR `@ ..` is not supported in struct patterns
     let Foo { bar @ .. } = foo; //~ ERROR `@ ..` is not supported in struct patterns