cleanup: remove unneeded source format in read instruction

The image crate is able to infer the format, so that data is redundant

crates/eval/src/kind/debug/instr/mod.rs

@@ -2,7 +2,7 @@ pub mod read {
     use image::{io::Reader as ImageReader, DynamicImage};
     use ir::instruction::read::{Read, SourceType};
 
-    pub fn read(Read { source, .. }: Read) -> DynamicImage {
+    pub fn read(Read { source }: Read) -> DynamicImage {
         // TODO: actual error handling
         let img = ImageReader::open(match source {
             SourceType::File(path) => path,

crates/ir/src/instruction/read.rs

@@ -4,16 +4,9 @@ use std::path::PathBuf;
 #[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash, Serialize, Deserialize)]
 pub struct Read {
     pub source: SourceType,
-    pub format: SourceFormat,
 }
 
 #[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash, Serialize, Deserialize)]
 pub enum SourceType {
     File(PathBuf),
 }
-
-#[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash, Serialize, Deserialize)]
-pub enum SourceFormat {
-    Jpeg,
-    Png,
-}

testfiles/bare.ron

@@ -2,7 +2,6 @@
 	instructions: {
 		0: Read((
 			source: File("testfiles/rails.png"),
-			format: Png,
 		)),
 		1: Write((
 			target: File("testfiles/gen/out.jpg"),

testfiles/invert.ron

@@ -2,7 +2,6 @@
 	instructions: {
 		0: Read((
 			source: File("testfiles/rails.png"),
-			format: Png,
 		)),
 		1: Filter(Invert),
 		2: Write((