Use ./gradlew for running UI tests on Linux.

Replaced `gradle` with `./gradlew` in the Linux workflow to ensure the correct Gradle wrapper is used consistently. This change aligns with best practices and improves compatibility across environments.

Author: VitaliyBoyko

.github/workflows/gradle.yml

@@ -19,7 +19,7 @@ jobs:
             runIde: |
               export DISPLAY=:99.0
               Xvfb -ac :99 -screen 0 1920x1080x16 &
-              gradle runIdeForUiTests &
+              ./gradlew runIdeForUiTests &
           - os: windows-latest
             runIde: start gradlew.bat runIdeForUiTests
           - os: macos-latest