fix newly introduced syntax errors

[lionralfs]

Summary

A few new syntax errors since #18442

This PR…
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• Adds a new document
• Rewrites (or significantly expands) a document
• Fixes a typo, bug, or other error

[github-actions]

Preview URLs

• https://pr18563.content.dev.mdn.mozit.cloud/en-US/docs/Web/API/VRPose/angularVelocity
• https://pr18563.content.dev.mdn.mozit.cloud/en-US/docs/Web/API/WEBGL_multi_draw
• https://pr18563.content.dev.mdn.mozit.cloud/en-US/docs/Web/API/WebGL_API/Tutorial/Using_shaders_to_apply_color_in_WebGL
• https://pr18563.content.dev.mdn.mozit.cloud/en-US/docs/Web/API/Web_Audio_API/Using_IIR_filters
• https://pr18563.content.dev.mdn.mozit.cloud/en-US/docs/Web/API/Window/showSaveFilePicker

Flaws

None! 🎉

External URLs

URL: /en-US/docs/Web/API/Window/showSaveFilePicker
Title: Window.showSaveFilePicker()
on GitHub

No new external URLs

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URL: /en-US/docs/Web/API/WebGL_API/Tutorial/Using_shaders_to_apply_color_in_WebGL
Title: Using shaders to apply color in WebGL
on GitHub

No new external URLs

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URL: /en-US/docs/Web/API/VRPose/angularVelocity
Title: VRPose.angularVelocity
on GitHub

No new external URLs

---

URL: /en-US/docs/Web/API/Web_Audio_API/Using_IIR_filters
Title: Using IIR filters
on GitHub

No new external URLs

---

URL: /en-US/docs/Web/API/WEBGL_multi_draw
Title: WEBGL_multi_draw
on GitHub

No new external URLs