Fix a few broken links (#87098)

References to headings need to be preceded with a slash. Also,
references to headings on the same page do not need to contain the name
of the document (omitting the document name means if the name changes
the links will still be valid).

I double checked the links by building [the
website](https://github.com/llvm/mlir-www):

```shell
./mlir-www-helper.sh --install-docs ../llvm-project website
cd website && hugo serve
```

mlir/docs/Tutorials/Toy/Ch-4.md

@@ -383,7 +383,7 @@ void MulOp::inferShapes() { getResult().setType(getLhs().getType()); }
 At this point, each of the necessary Toy operations provide a mechanism by which
 to infer their output shapes. The ShapeInferencePass will operate on functions:
 it will run on each function in isolation. MLIR also supports general
-[OperationPasses](../../PassManagement.md#operation-pass) that run on any
+[OperationPasses](../../PassManagement.md/#operation-pass) that run on any
 isolated operation, but here our module only contains functions, so there is no
 need to generalize to all operations.
 

mlir/docs/Tutorials/transform/Ch4.md

@@ -27,7 +27,7 @@ directly within the transform dialect.
 ## Simple match
 
 Let us reconsider the “fully connected layer” example from [Chapter
-1](Ch1.md#chaining-transformations-with-handles), reproduced below for
+1](Ch1.md/#chaining-transformations-with-handles), reproduced below for
 convenience.