fs/io/BufferedOutputStream: add `noexcept`

src/fs/io/BufferedOutputStream.hxx

@@ -53,7 +53,7 @@ class BufferedOutputStream {
 	DynamicFifoBuffer<char> buffer;
 
 public:
-	explicit BufferedOutputStream(OutputStream &_os)
+	explicit BufferedOutputStream(OutputStream &_os) noexcept
 		:os(_os), buffer(32768) {}
 
 	void Write(const void *data, size_t size);