chore(ci): update codeowners (#15093)

## Description

give ownership to test file for iast to asm team.

APPSEC-59813

Author: christophe-papazian

.github/CODEOWNERS

@@ -126,6 +126,7 @@ tests/appsec/                       @DataDog/asm-python
 tests/contrib/subprocess            @DataDog/asm-python
 tests/snapshots/tests*appsec*.json  @DataDog/asm-python
 tests/contrib/*/test*appsec*.py     @DataDog/asm-python
+tests/contrib/*/test*iast*.py  @DataDog/asm-python
 scripts/iast/*                      @DataDog/asm-python
 
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