Revert "Treat blocks with "return" as "noreturn""

This reverts commit 135b91aecd9be1f6f5806b667e07e383dd481198.

"endsWithBreak()" is not a meaningful question to ask and should not be
used this way. A simple example that defeats this logic is:

```zig
export fn entry() void {
    outer: {
        {
            break :outer;
        }
        return;
    }
}
```

1 files changed, 0 insertions, 10 deletions

diff --git a/src/AstGen.zig b/src/AstGen.zig
index 21e5170030..ab5befa4ba 100644
--- a/src/AstGen.zig
+++ b/src/AstGen.zig
@@ -1967,9 +1967,6 @@ fn blockExpr(
     }
 
     try blockExprStmts(gz, scope, statements);
-    if (gz.endsWithNoReturn() and !gz.endsWithBreak()) {
-        return Zir.Inst.Ref.unreachable_value;
-    }
     return rvalue(gz, rl, .void_value, block_node);
 }
 
@@ -9933,13 +9930,6 @@ const GenZir = struct {
         return tags[last_inst].isNoReturn();
     }
 
-    fn endsWithBreak(gz: GenZir) bool {
-        if (gz.isEmpty()) return false;
-        const tags = gz.astgen.instructions.items(.tag);
-        const last_inst = gz.instructions.items[gz.instructions.items.len - 1];
-        return tags[last_inst].isBreak();
-    }
-
     /// TODO all uses of this should be replaced with uses of `endsWithNoReturn`.
     fn refIsNoReturn(gz: GenZir, inst_ref: Zir.Inst.Ref) bool {
         if (inst_ref == .unreachable_value) return true;