Validation of `$removeheader` prevents adding some rules

[Alex-302]

Please answer the following questions for yourself before submitting an issue

• [X] Filters were updated before reproducing an issue
• [X] I checked the knowledge base and found no answer
• [X] I checked to make sure that this issue has not already been filed

AdGuard version

7.18.0 n4

Browser version

Chrome

OS version

Windows 10 x64

Traffic filtering

• [X] yes, I do

Ad Blocking

AdGuard Base filter

Privacy

No response

Social

No response

Annoyances

No response

Security

No response

Other

No response

Language-specific

No response

Which DNS server do you use?

System default DNS

DNS protocol

Regular

Custom DNS

No response

What Stealth Mode options do you have enabled?

No response

Support ticket ID

No response

Issue Details

Steps to reproduce:

1. Try to add googlevideo.com^$removeheader=Content-Type

Expected Behavior

The rule added.

Actual Behavior

The rule is not added. But googlevideo.com^$removeheader=Test-Test can be added.

Screenshots

Screenshot 1

Additional Information

No response