DocsUI: Disable lint for tests because it's crashing

The lint for this test target started crashing in the Mainline module
builder. Disabling until it gets fixed.

Bug: 439453044, 439566448
Flag: EXEMPT test/lint
Test: Build:  build/soong/soong_ui.bash --make-mode -j64 \
 TARGET_PRODUCT=mainline_modules_x86_64 \
 DIST_DIR=out/dist/mainline_modules_x86_64 \
 'TARGET_BUILD_APPS=DocumentsUIGoogle DocumentsUIGoogleTests ' \
 ALWAYS_EMBED_NOTICES=true MODULE_BUILD_FROM_SOURCE=true \
 EMMA_INSTRUMENT=true EMMA_INSTRUMENT_FRAMEWORK=true \
 CLANG_COVERAGE=true CLANG_COVERAGE_CONTINUOUS_MODE=false \
 ANDROID_LINT_CHECK=JavaKotlinApiUsedByModule \
 ANDROID_LINT_CHECK_EXTRA_MODULES=JavaKotlinApiFinder \
 SOONG_COLLECT_JAVA_DEPS=true APEX_BUILD_FOR_PRE_S_DEVICES=true \
 out/host/linux-x86/bin/merge_zips lint-check module-info apps_only dist
Change-Id: Ic6c55312c1a94cd66849585c70eac9eb587f2c7a