chore/docs: improve wording and fix typos (#5157)

## Description

Smol docs update. Fixes:

- A typo in assembly docs.
- A typo in unit testing docs.
- Couple of code documentation typos.

docs/book/src/advanced/assembly.md

@@ -23,7 +23,7 @@ pub fn add_1(num: u32) -> u32 {
 }
 ```
 
-An `asm` block can only return a single register. If you really need to return more than one value, you can modify a tuple. Here's an example showing how can implement this `(u64, u64)`:
+An `asm` block can only return a single register. If you really need to return more than one value, you can modify a tuple. Here's an example showing how you can implement this `(u64, u64)`:
 
 ```sway
 {{#include ../../../../examples/asm_return_tuple_pointer/src/main.sw}}

docs/book/src/testing/unit-testing.md

@@ -117,7 +117,7 @@ fn test_fail() {
 > **Note:** When running `forc test`, your contract will be built twice: first *without* unit tests in order to determine the contract's ID, then a second time *with* unit tests with the `CONTRACT_ID` provided to their namespace. This `CONTRACT_ID` can be used with the `abi` cast to enable contract calls within unit tests.
 <!-- contract_id:example:end -->
 
-Unit tests can call methods of external contracts if those contracts are added as contract dependencies, i.e. in the the [`contract-dependencies`](../forc/manifest_reference.md#the-contract-dependencies-section) section of the manifest file. An example of such calls is shown below:
+Unit tests can call methods of external contracts if those contracts are added as contract dependencies, i.e. in the [`contract-dependencies`](../forc/manifest_reference.md#the-contract-dependencies-section) section of the manifest file. An example of such calls is shown below:
 
 ```sway
 {{#include ../../../../examples/multi_contract_calls/caller/src/main.sw:multi_contract_calls}}

sway-core/src/asm_generation/evm/evm_asm_builder.rs

@@ -176,7 +176,7 @@ impl<'ir, 'eng> EvmAsmBuilder<'ir, 'eng> {
         self.setup_free_memory_pointer(&mut s);
 
         if is_payable {
-            // Get the the amount of ETH transferred to the contract by the parent contract,
+            // Get the amount of ETH transferred to the contract by the parent contract,
             // or by a transaction and check for a non-payable contract. Revert if caller
             // sent ether.
             //

sway-core/src/language/ty/declaration/declaration.rs

@@ -733,7 +733,7 @@ impl TyDecl {
     }
 
     /// friendly name string used for error reporting,
-    /// which consists of the the identifier for the declaration.
+    /// which consists of the identifier for the declaration.
     pub fn friendly_name(&self, engines: &Engines) -> String {
         let decl_engine = engines.de();
         let type_engine = engines.te();