Fix:update specification of claude v2 modelid

[sho-saito]

Issue #235, if available:

Description of changes:

In attempting to correct this,
I assume this part

rain/internal/aws/bedrock/bedrock.go

Lines 30 to 33 in 10c3391

	const (
	claudePromptFormat = "\n\nHuman:%s\n\nAssistant:"
	claudeV2ModelID = "anthropic.claude-v2"
	)

could be modified by specifying :1 at the end of claudeV2ModelID as follows

const (
	claudePromptFormat = "\n\nHuman:%s\n\nAssistant:"
	claudeV2ModelID    = "anthropic.claude-v2:1"
)

When I tried the modified one, it actually worked like this

$ ./rain build -p "VPC with 1 private and 1 public subnet"
AWSTemplateFormatVersion: '2010-09-09'
Description: VPC with 1 public and 1 private subnet

Resources:

  VPC:
    Type: AWS::EC2::VPC
    Properties:
      CidrBlock: 10.0.0.0/16
      EnableDnsSupport: true
      EnableDnsHostnames: true
  
  PublicSubnet:
    Type: AWS::EC2::Subnet
    Properties:
      VpcId: !Ref VPC
      CidrBlock: 10.0.1.0/24
      MapPublicIpOnLaunch: true
  
  PrivateSubnet:
    Type: AWS::EC2::Subnet
    Properties: 
      VpcId: !Ref VPC
      CidrBlock: 10.0.2.0/24

reference:
https://docs.aws.amazon.com/bedrock/latest/userguide/model-ids-arns.html#:~:text=anthropic.claude%2Dv2.%20For%20Claude%202.1%2C%20use%20anthropic.claude%2Dv2%3A1

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