fix: Changed the table name in delete item to use client tablename (#8)

## Description:

### Changes Made:
The deleteItem function is currently relying on the table name fetched
from the environment variable. This requires the maintenance of a
separate variable named DYNAMODB_TABLE for the function to operate
correctly. To align with the consistency of the codebase and ensure
uniformity, I have made modifications to the function. The updated
implementation now utilizes the table name configured for the DynamoDB
client, bringing it in line with the approach adopted by other
functions. This adjustment addresses an oversight where the deleteItem
function was not following the same convention as other functions in
handling the DynamoDB table name.

Key Points:

### Before:

deleteItem function used the table name from the DYNAMODB_TABLE
environment variable.
Required a separate variable (DYNAMODB_TABLE) for correct functionality.
### After:

Modified deleteItem to use the table name configured for the DynamoDB
client.
Ensures consistency with other functions in the codebase.
Reason for the Change:
To maintain code consistency and streamline the usage of DynamoDB table
names across functions. This change eliminates the need for a separate
environment variable (DYNAMODB_TABLE) specific to the deleteItem
function, aligning it with the established configuration pattern used by
other functions.

## Related Issues:
#9

delete_item.go

@@ -3,7 +3,6 @@ package dynago
 import (
 	"context"
 	"log"
-	"os"
 
 	"github.com/aws/aws-sdk-go-v2/service/dynamodb"
 	"github.com/aws/aws-sdk-go-v2/service/dynamodb/types"
@@ -16,11 +15,10 @@ import (
  * @return true if the record was deleted, false otherwise
 */
 func (t *Client) DeleteItem(ctx context.Context, pk string, sk string) error {
-	table := os.Getenv("DYNAMODB_TABLE")
 
 	//delete item from dynamodb
 	input := &dynamodb.DeleteItemInput{
-		TableName: &table,
+		TableName: &t.TableName,
 		Key: map[string]types.AttributeValue{
 			"pk": &types.AttributeValueMemberS{Value: pk},
 			"sk": &types.AttributeValueMemberS{Value: sk},