doc: Fix alt text in widgets.md

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What does this MR do and why?

Related to: #479161

Improves alt text for license compliance widget for easy accessibility.

Changes made

• updated the irrelevant and duplicated text from "Merge request pipeline" to "License compliance widget"

Before:

![Merge request pipeline](img/license_compliance_widget_v15_3.png)

After:

![License compliance widget](img/license_compliance_widget_v15_3.png)

References

Screenshots or screen recordings

Before	After

How to set up and validate locally

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