config: document includeIf conditions consistently

config: document includeIf conditions consistently

When 399b1984 (config: include file if remote URL matches a glob,
2022-01-18) added the 'hasconfig:remote.*.url:<URL>' condition to be
used in the "includeIf.<condition>.path" configuration, the keyword
was added with an extra colon in the documentation.

The section that documents these condition begins with this preamble:

    The condition starts with a keyword followed by a colon and some data
    whose format and meaning depends on the keyword. Supported keywords
    are:

which makes it clear that the colon that comes between the condition
keyword (e.g. "gitdir") and the parameter (aka "some data") is not
a part of the keyword.

Lose the extra colon.  Also rewrite description of all keywords to
clarify that "some data" does not directly follow "keyword", and the
colon is not a part of keyword.

Signed-off-by: Junio C Hamano <gitster@pobox.com>