Fix typos in the quick help of files (#3837)

### Goals ⚽
<!-- List the high-level objectives of this pull request. -->
<!-- Include any relevant context. -->
- Fix typos in the quick help of `Request.swift`,
`ResponseSerialization.swift`, `ServerTrustEvaluation.swift`,
`URLEncodedFormEncoder.swift`

### Implementation Details 🚧
<!-- Explain the reasoning behind any architectural changes. -->
<!-- Highlight any new functionality. -->
1. `Request.swift` -> `isResumed`

|before|after|
|--|--|
|<img width="350"
src="https://github.com/Alamofire/Alamofire/assets/51712973/8a5b9abf-2d66-460d-b831-d5d9ce3f48f9">|<img
width="350"
src="https://github.com/Alamofire/Alamofire/assets/51712973/68797322-15aa-4ba2-896f-75b3bb757720">|

2. `ResponseSerialization.swift` ->
`responseAllowsEmptyResponseData(_:)`

|before|after|
|--|--|
|<img width="350"
src="https://github.com/Alamofire/Alamofire/assets/51712973/ceb68e06-19bb-4f3a-a8fa-261fdf646d9f">|<img
width="350"
src="https://github.com/Alamofire/Alamofire/assets/51712973/4cd98ceb-8de9-4cab-9879-969453536a4f">|

3. `ServerTrustEvaluation.swift` -> `AlamofireExtension` -> `isSuccess`

|before|after|
|--|--|
|<img width="350"
src="https://github.com/Alamofire/Alamofire/assets/51712973/aa5ca255-9893-48bc-8a4d-e77a9735eb40">|<img
width="350"
src="https://github.com/Alamofire/Alamofire/assets/51712973/43180633-4019-47c1-8556-e9ed2610426e">|

4. `URLEncodedFormEncoder.swift` -> `encode(_:)`

|before|after|
|--|--|
|<img width="350"
src="https://github.com/Alamofire/Alamofire/assets/51712973/44f0b62f-83c3-4bdf-a126-37a436eef10d">|<img
width="350"
src="https://github.com/Alamofire/Alamofire/assets/51712973/b3fee803-6bbd-4aca-941e-1551d99f565f">|


### Testing Details 🔍
<!-- Describe what tests you've added for your changes. -->
No testing is needed as the change is in the comment.

Source/Core/Request.swift

@@ -131,7 +131,7 @@ public class Request {
  public var state: State { mutableState.state }
  /// Returns whether `state` is `.initialized`.
  public var isInitialized: Bool { state == .initialized }
- /// Returns whether `state is `.resumed`.
+ /// Returns whether `state` is `.resumed`.
  public var isResumed: Bool { state == .resumed }
  /// Returns whether `state` is `.suspended`.
  public var isSuspended: Bool { state == .suspended }

Source/Features/ResponseSerialization.swift

@@ -128,7 +128,7 @@ extension ResponseSerializer {
  .map { emptyRequestMethods.contains($0) }
  }
 
- /// Determines whether the `response` allows empty response bodies, if `response` exists`.
+ /// Determines whether the `response` allows empty response bodies, if `response` exists.
  ///
  /// - Parameter response: `HTTPURLResponse` to evaluate.
  ///

Source/Features/ServerTrustEvaluation.swift

@@ -760,7 +760,7 @@ extension AlamofireExtension where ExtendedType == OSStatus {
 
 extension SecTrustResultType: AlamofireExtended {}
 extension AlamofireExtension where ExtendedType == SecTrustResultType {
- /// Returns whether `self is `.unspecified` or `.proceed`.
+ /// Returns whether `self` is `.unspecified` or `.proceed`.
  public var isSuccess: Bool {
  type == .unspecified || type == .proceed
  }

Source/Features/URLEncodedFormEncoder.swift

@@ -445,7 +445,7 @@ public final class URLEncodedFormEncoder {
 
  /// Encodes the `value` as a URL form encoded `String`.
  ///
- /// - Parameter value: The `Encodable` value.`
+ /// - Parameter value: The `Encodable` value.
  ///
  /// - Returns: The encoded `String`.
  /// - Throws: An `Error` or `EncodingError` instance if encoding fails.