fix: amount to receive

[wainola]

Description

Fixes displayed amount to receive due to double subtraction over the already subtracted value

Related Issue Or Context

Closes: #192

How Has This Been Tested? Testing details.

Types of changes

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)
• [ ] Documentation

Checklist:

• [ ] I have commented my code, particularly in hard-to-understand areas.
• [ ] I have ensured that all acceptance criteria (or expected behavior) from issue are met
• [ ] I have updated the documentation locally and in sygma-docs.
• [ ] I have added tests to cover my changes.
• [ ] I have ensured that all the checks are passing and green, I've signed the CLA bot

[wainola]

update: as per conversation with @sztok7 I'm going to make a small refactor to avoid the checking and also rely on debounce for the race conditions when building the transfers

[LyonSsS]

Currently there are 2 issues on it:

1. Source Substrate it breaks after using it several time STR:

2. Select source Rahala

3. Destination Sepolia

4. Select SygUSDC as token

5. Fill in destination wallet.

6. Fill in amount.

7. After switching to many times the input value, it will lose track to update This issue is not consistent and does not have 100% chance to replicate.

[LyonSsS]

Re tested and there is still an issue: When switching to a new network source, that requires the user to reset the token type drop down, if the user inputs a 2 digit number very fast, the "Amount to receive:" is only going to be calculated only from the first digit number. See gif below

[LyonSsS]

There is still a small issue ongoing as:

STR:

1. Select Sepolia source and destination Base.
2. Connect Metmask wallet.
3. Insert value 25 and then paste the destination EVM address.
4. Then switch destination to Rococo.
5. Insert a value destination address and wait for math to update.
6. Then switch destination to Base one more and wait for math to update.
7. Then switch destination to Rhala again.
8. Update the amount to be transfered from 25 to 4 and then insert the destination Rhala Address. Booth action very fast ( <= 1 second).

Exp: The amount to be transferred to be set to the new input ( value 4 - Fee). Act: The amount to be transferred is calculated based on the initial input - 25.

[saadahmsiddiqui]

There is still a small issue ongoing as:

STR:

1. Select Sepolia source and destination Base.
2. Connect Metmask wallet.
3. Insert value 25 and then paste the destination EVM address.
4. Then switch destination to Rococo.
5. Insert a value destination address and wait for math to update.
6. Then switch destination to Base one more and wait for math to update.
7. Then switch destination to Rhala again.
8. Update the amount to be transfered from 25 to 4 and then insert the destination Rhala Address. Booth action very fast ( <= 1 second).

Exp: The amount to be transferred to be set to the new input ( value 4 - Fee). Act: The amount to be transferred is calculated based on the initial input - 25.

We would like to close this PR as this case occurs when a very fast reaction is made from the user, we can open an issue in future if we can easily reproduce this