Revert "defer changes for zero argument functions until style_edition=2027"

This effectively reverts commit
a7e0c15.

This change made it into the 2024 style edition so we can't defer it to
2027.

Author: ytmimi

src/items.rs

@@ -2569,7 +2569,7 @@ fn rewrite_fn_base(
             .last()
             .map_or(false, |last_line| last_line.contains("//"));
 
-        if context.config.style_edition() >= StyleEdition::Edition2027 {
+        if context.config.style_edition() >= StyleEdition::Edition2024 {
             if closing_paren_overflow_max_width {
                 result.push(')');
                 result.push_str(&indent.to_string_with_newline(context.config));

tests/source/issue-3278/style_edition_2015.rs renamed to tests/source/issue-3278/version_one.rs

@@ -1,4 +1,4 @@
-// rustfmt-style_edition: 2027
+// rustfmt-style_edition: 2024
 
 pub fn parse_conditional<'a, I: 'a>()
 -> impl Parser<Input = I, Output = Expr, PartialState = ()> + 'a

tests/source/issue-3278/style_edition_2024.rs renamed to tests/source/issue-3278/version_two.rs

@@ -1,4 +1,4 @@
-// rustfmt-style_edition: 2027
+// rustfmt-style_edition: 2024
 // Tests that a function which is almost short enough, but not quite, gets
 // formatted correctly.