common: fs: file: Remove [[nodiscard]] attribute from Flush

Similarly, Flush() is typically called to attempt to flush a file into the disk. In the one case where this is used, we do not care whether the flush has succeeded or not, making [[nodiscard]] unnecessary.

src/common/fs/file.h

@@ -394,11 +394,11 @@ public:
     [[nodiscard]] size_t WriteString(std::span<const char> string) const;
 
     /**
-     * Flushes any unwritten buffered data into the file.
+     * Attempts to flush any unwritten buffered data into the file and flush the file into the disk.
      *
      * @returns True if the flush was successful, false otherwise.
      */
-    [[nodiscard]] bool Flush() const;
+    bool Flush() const;
 
     /**
      * Resizes the file to a given size.

src/common/logging/backend.cpp

@@ -186,7 +186,7 @@ void FileBackend::Write(const Entry& entry) {
 
     bytes_written += file->WriteString(FormatLogMessage(entry).append(1, '\n'));
     if (entry.log_level >= Level::Error) {
-        void(file->Flush());
+        file->Flush();
     }
 }