Drop showing indent level number in DEFAULT prompt and INF_RUBY prompt

[tompng]

Removes indent level number in :DEFAULT and :INF_RUBY prompt mode.

irb(main):001:1> if true
irb(main):002:2>   puts(
irb(main):003:3>     1,
irb(main):004:3>     2,
↓
irb(main):001> if true
irb(main):002>   puts(
irb(main):003>     1,
irb(main):004>     2,

Until irb 1.0.0, auto indent was not enabled by default and this indent level number was useful.

irb(main):001:0> IRB::VERSION
=> "1.0.0"
irb(main):002:0> def f
irb(main):003:1> if true
irb(main):004:2> puts(
irb(main):005:3* 1,
irb(main):006:3* 2,
irb(main):007:3* )
irb(main):008:2> end
irb(main):009:1> end
=> :f

But now, auto indent is enabled by default. Indent level is identical to next-line's indentation spaces. You can easily know how deep the code is nested without seeing this number. It is just making prompt long.

Other prompt modes

For :INF_RUBY prompt mode, only PROMPT_I is present. In this case, indent level number (always zero) is completely useless.
Indent level number still remains in :CLASSIC prompt mode.

[st0012]

Love it 😍