Remove instances of required arguments with default values (sigp#4489)

## Issue Addressed

sigp#4488 

## Proposed Changes

 - Remove all instances of the `required` modifier where we have a default value specified for a subcommand

## Additional Info

N/A

lcli/src/main.rs

@@ -39,7 +39,6 @@ fn main() {
                 .long("spec")
                 .value_name("STRING")
                 .takes_value(true)
-                .required(true)
                 .possible_values(&["minimal", "mainnet", "gnosis"])
                 .default_value("mainnet")
                 .global(true),
@@ -371,7 +370,6 @@ fn main() {
                         .index(2)
                         .value_name("BIP39_MNENMONIC")
                         .takes_value(true)
-                        .required(true)
                         .default_value(
                             "replace nephew blur decorate waste convince soup column \
                             orient excite play baby",
@@ -392,7 +390,6 @@ fn main() {
                         .help("The block hash used when generating an execution payload. This \
                             value is used for `execution_payload_header.block_hash` as well as \
                             `execution_payload_header.random`")
-                        .required(true)
                         .default_value(
                             "0x0000000000000000000000000000000000000000000000000000000000000000",
                         ),
@@ -410,7 +407,6 @@ fn main() {
                         .value_name("INTEGER")
                         .takes_value(true)
                         .help("The base fee per gas field in the execution payload generated.")
-                        .required(true)
                         .default_value("1000000000"),
                 )
                 .arg(
@@ -419,7 +415,6 @@ fn main() {
                         .value_name("INTEGER")
                         .takes_value(true)
                         .help("The gas limit field in the execution payload generated.")
-                        .required(true)
                         .default_value("30000000"),
                 )
                 .arg(