chore(gatsby-source-contentful): Fix docs pageLimit default value

[fk]

Fix gatsby-source-contentful docs for the pageLimit configuration option.
Its default value is 1000, not 100:

gatsby/packages/gatsby-source-contentful/src/plugin-options.js

Lines 5 to 17 in cbc0b35

	const DEFAULT_PAGE_LIMIT = 1000
	const defaultOptions = {
	host: `cdn.contentful.com`,
	environment: `master`,
	downloadLocal: false,
	localeFilter: () => true,
	contentTypeFilter: () => true,
	pageLimit: DEFAULT_PAGE_LIMIT,
	useNameForId: true,
	enableTags: false,
	typePrefix: `Contentful`,
	}

[fk]

ty @LekoArts! <3