Bug: [BUG] using FRM with Signifyd throws 5xx



### Bug Description

Enabling Signifyd FRM connector for payments, and using this for a payment throws 5xx. This is due to Signifyd sending 303 which is not handled in HyperSwitch. Signifyd throws 303 as the URL is malformed.

https://api.signifyd.com//v3/orders/events/sales as opposed to https://api.signifyd.com/v3/orders/events/sales

### Expected Behavior

Calling any Signifyd API should return an expected status code.

### Actual Behavior

Calling any Signifyd API returns 303 - which is not handled in the response handler of `execute_connector_processing_step` leading to 500 - Something went wrong.

### Steps To Reproduce

1. Enable FRM via Signifyd for a payment connector
2. Create a payment
3. 5xx is thrown in API response


### Have you spent some time checking if this bug has been raised before?

- [X] I checked and didn't find a similar issue

### Have you read the Contributing Guidelines?

- [X] I have read the [Contributing Guidelines](https://github.com/juspay/hyperswitch/blob/main/docs/CONTRIBUTING.md)

### Are you willing to submit a PR?

Yes, I am willing to submit a PR!
diff --git a/crates/router/src/connector/signifyd.rs b/crates/router/src/connector/signifyd.rs
index 6ba2dce9861..4ee36d8966b 100644
--- a/crates/router/src/connector/signifyd.rs
+++ b/crates/router/src/connector/signifyd.rs
@@ -237,7 +237,7 @@ impl
         Ok(format!(
             "{}{}",
             self.base_url(connectors),
-            "/v3/orders/events/sales"
+            "v3/orders/events/sales"
         ))
     }
 
@@ -325,7 +325,7 @@ impl
         Ok(format!(
             "{}{}",
             self.base_url(connectors),
-            "/v3/orders/events/checkouts"
+            "v3/orders/events/checkouts"
         ))
     }
 
@@ -413,7 +413,7 @@ impl
         Ok(format!(
             "{}{}",
             self.base_url(connectors),
-            "/v3/orders/events/transactions"
+            "v3/orders/events/transactions"
         ))
     }
 
@@ -503,7 +503,7 @@ impl
         Ok(format!(
             "{}{}",
             self.base_url(connectors),
-            "/v3/orders/events/fulfillments"
+            "v3/orders/events/fulfillments"
         ))
     }
 
@@ -593,7 +593,7 @@ impl
         Ok(format!(
             "{}{}",
             self.base_url(connectors),
-            "/v3/orders/events/returns/records"
+            "v3/orders/events/returns/records"
         ))
     }
 

## Type of Change
<!-- Put an `x` in the boxes that apply -->

- [x] Bugfix
- [ ] New feature
- [ ] Enhancement
- [ ] Refactoring
- [ ] Dependency updates
- [ ] Documentation
- [ ] CI/CD

## Description
Described in #5956 

### Additional Changes

- [ ] This PR modifies the API contract
- [ ] This PR modifies the database schema
- [ ] This PR modifies application configuration/environment variables

<!--
Provide links to the files with corresponding changes.

Following are the paths where you can find config files:
1. `config`
2. `crates/router/src/configs`
3. `loadtest/config`
-->


## Motivation and Context
Fixes 5xx thrown by payments API when FRM flows are consumed.


## How did you test it?
Locally - using an increased stack size.


## Checklist
<!-- Put an `x` in the boxes that apply -->

- [x] I formatted the code `cargo +nightly fmt --all`
- [x] I addressed lints thrown by `cargo clippy`
- [x] I reviewed the submitted code
- [ ] I added unit tests for my changes where possible
