minor typo fixes (#445)

* typo fix

how to expose the them to any sort of external testing apparatus
=> how to expose them to any sort of external testing apparatus

* typo fix

These following image depicts
=> The following image depicts

* typo fix

trait itself is found in in 
=> trait itself is found in

* Update src/mir/passes.md

following JohnTitor's suggestion

Co-Authored-By: Yuki Okushi <huyuumi.dev@gmail.com>

* Update src/test-implementation.md

Also following JohnTitor's suggestion

Co-Authored-By: Yuki Okushi <huyuumi.dev@gmail.com>

src/mir/construction.md

@@ -92,7 +92,7 @@ There are essentially four kinds of representations one might want of an express
 * `Operand` is an argument to e.g. a `+` operation or a function call
 * a temporary variable containing a copy of the value
 
-These following image depicts a general overview of the interactions between the
+The following image depicts a general overview of the interactions between the
 representations:
 
 <img src="mir_overview.svg">

src/mir/passes.md

@@ -27,7 +27,7 @@ where we want to access the MIR for type checking or other purposes:
 A `MirPass` is some bit of code that processes the MIR, typically –
 but not always – transforming it along the way somehow. For example,
 it might perform an optimization. The `MirPass` trait itself is found
-in in [the `rustc_mir::transform` module][mirtransform], and it
+in [the `rustc_mir::transform` module][mirtransform], and it
 basically consists of one method, `run_pass`, that simply gets an
 `&mut Mir` (along with the tcx and some information about where it
 came from). The MIR is therefore modified in place (which helps to

src/test-implementation.md

@@ -25,7 +25,7 @@ mod my_priv_mod {
 }
 ```
 Private items can thus be easily tested without worrying about how to expose
-the them to any sort of external testing apparatus. This is key to the
+them to any sort of external testing apparatus. This is key to the
 ergonomics of testing in Rust. Semantically, however, it's rather odd.
 How does any sort of `main` function invoke these tests if they're not visible?
 What exactly is `rustc --test` doing?