Show line numbers only when showLineNumbers == true

[AbhyudayaSharma]

After updating to 14.0.0, I started seeing line numbers for code blocks of a single line even when showLineNumbers was unset. One potential walkaround I found was to explicitly set showInlineLineNumbers = false. But this PR fixes the problem with unwrapped lines by only showing line numbers if showLineNumbers == true.

This is how I was using SyntaxHighlighter:

<SyntaxHighlighter language={language || 'text'} style={darcula}>
  {this.props.value}
</SyntaxHighlighter>

Before:

After:

I think there exists a similar bug when wrapLongLines == true but this PR does not fix that.

[simmerer]

Thank you for this!