doc: happy-eyeballs text is awkward

[jsoref]

curl/docs/cmdline-opts/happy-eyeballs-timeout-ms.d

Lines 8 to 9 in f538bc5

	addresses for dual-stack hosts, preferring IPv6 first for the number of
	milliseconds. If the IPv6 address cannot be connected to within that time then

... preferring IPv6 first for the number of milliseconds ...

is awkward.

I suspect it could be improved by changing preferring...first to giving IPv6 a head-start of ....

I'm familiar w/ happy-eyeballs technically, but the text here is confusing.

curl/docs/cmdline-opts/happy-eyeballs-timeout-ms.d

Line 7 in f538bc5

Happy eyeballs is an algorithm that attempts to connect to both IPv4 and IPv6

Beyond that, Happy Eyeballs should probably be capitalized as such. c.f.

curl/docs/cmdline-opts/happy-eyeballs-timeout-ms.d

Line 13 in f538bc5

The range of suggested useful values is limited. Happy Eyeballs RFC 6555 says

Unless there's a house style I haven't properly identified.

Possible text:

Happy Eyeballs is an algorithm that attempts to connect to both IPv4 and IPv6 addresses for dual-stack hosts, giving IPv6 a head-start of the specified number of milliseconds.