Don't update missing requirements.txt (#1013)

image_generation was removed. There's nothing to update in root
project.toml. ./tests/python_tests/ update fails with an error that it
can't resolve the path, but maybe it gets fixed later, so keep it.

.github/dependabot.yml

@@ -1,19 +1,15 @@
 version: 2
 updates:
   - package-ecosystem: "pip"
-    directory: "./"
-    schedule:
-      interval: "weekly"
-  - package-ecosystem: "pip"
-    directory: "image_generation/stable_diffusion_1_5/cpp/scripts/"
+    directory: "./tests/python_tests/"
     schedule:
       interval: "weekly"
   - package-ecosystem: "pip"
-    directory: "image_generation/lcm_dreamshaper_v7/cpp/scripts/"
+    directory: "./tools/llm_bench/"
     schedule:
       interval: "weekly"
   - package-ecosystem: "pip"
-    directory: "./tests/python_tests/"
+    directory: "./tools/who_what_benchmark/"
     schedule:
       interval: "weekly"
   - package-ecosystem: "pip"