Update image-no-text assumption (#2149)

* Update image-no-text assumption

As discussed here: w3c/wcag#3549 (reply in thread)

* Update _rules/image-no-text-0va7u6.md

Co-authored-by: Dan Bjorge <dan@dbjorge.net>

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Co-authored-by: Dan Bjorge <dan@dbjorge.net>

Author: WilcoFiers

_rules/image-no-text-0va7u6.md

@@ -45,8 +45,7 @@ Each test target has no [visible][] [text][human language], except if at least o
 
 ## Assumptions
 
-- There is no mechanism to change the rendered text in the image resource. Otherwise, the rule might fail while [SC 1.4.5 Images of Text][sc1.4.5] might be satisfied.
-- The specific presentation of the text rendered in the image resource can be achieved through formatted text. Otherwise, the rule might fail while [SC 1.4.5 Images of Text][sc1.4.5] might be satisfied.
+- This rule assumes that there is no mechanism to change the rendering of text within image resources on the page. For pages that *do* provide such a mechanism, this rule might fail even if [SC 1.4.5 Images of Text][sc1.4.5] is satisfied.
 - When used in HTML, the SVG `<text>` element is not considered to be an image of text. This is because like any other element in HTML, SVG `<text>` can be adjusted through custom style sheets. This does not apply for SVG text that is in a separate file, and displayed through, for example, the `img` element.
 
 ## Accessibility Support