read/macho: delete unused DyldCacheImageInfo::file_offset

This is leftover from before subcaches were supported.

src/read/macho/dyld_cache.rs

@@ -908,24 +908,14 @@ impl<E: Endian> macho::DyldCacheHeader<E> {
 
 impl<E: Endian> macho::DyldCacheImageInfo<E> {
     /// The file system path of this image.
+    ///
+    /// `data` should be the main cache file, not the subcache containing the image.
     pub fn path<'data, R: ReadRef<'data>>(&self, endian: E, data: R) -> Result<&'data [u8]> {
         let r_start = self.path_file_offset.get(endian).into();
         let r_end = data.len().read_error("Couldn't get data len()")?;
         data.read_bytes_at_until(r_start..r_end, 0)
             .read_error("Couldn't read dyld cache image path")
     }
-
-    /// Find the file offset of the image by looking up its address in the mappings.
-    pub fn file_offset<'data, R: ReadRef<'data>>(
-        &self,
-        endian: E,
-        mappings: &DyldCacheMappingSlice<'data, E, R>,
-    ) -> Result<u64> {
-        let address = self.address.get(endian);
-        mappings
-            .address_to_file_offset(address)
-            .read_error("Invalid dyld cache image address")
-    }
 }
 
 impl<E: Endian> macho::DyldCacheMappingAndSlideInfo<E> {