Update cf-mgmt-config global documentation

[Petahhh]

Describe the solution you'd like

• The cf-mgmt-config global README.md should match the output from running cf-mgmt-config global --help command.
• The output from cf-mgmt-config global --help does not seem to be complete.
  • The --no-access-plan flag contains the same description as --all-access-plan=

Sample output:

>cf-mgmt-config global --help
error: Usage:
  cf-mgmt-config [OPTIONS] global [global-OPTIONS]

Help Options:
  -h, --help                                              Show this help message

[global command options]
          --config-dir=                                   Name of the config directory
                                                          (default: config) [$CONFIG_DIR]
          --enable-delete-isolation-segments=[true|false] Enable removing isolation
                                                          segments
          --enable-delete-shared-domains=[true|false]     Enable removing shared domains
          --enable-service-access=[true|false]            Enable managing service access
          --enable-unassign-security-groups=[true|false]  Enable unassigning security
                                                          groups
          --metadata-prefix=                              Prefix for org/space metadata
          --staging-security-group=                       Staging Security Group to add
          --remove-staging-security-group=                Staging Security Group to remove
          --running-security-group=                       Running Security Group to add
          --remove-running-security-group=                Running Security Group to remove
          --shared-domain=                                Shared Domain to add
          --router-group-shared-domain=                   Router Group Shared Domain to
                                                          add
          --router-group-shared-domain-group=             Router Group Shared Domain group
          --internal-shared-domain=                       Internal Shared Domain to add
          --remove-shared-domain=                         Shared Domain to remove

    service-access:
          --broker=                                       Name of Broker
          --service=                                      Name of Service
          --all-access-plan=                              Plan to give access to all orgs
          --limited-access-plan=                          Plan to give limited access to,
                                                          must also provide org list
          --org=                                          Orgs to add to limited plan
          --remove-org=                                   Orgs to remove from limited plan
          --no-access-plan=                               Plan to give access to all orgs

[hsinn0]

Merged the PR.