ci: disable uv caching

we don't use lock file, so setup-uv falls back on "empty" cache key which can result in misleading dependency versions

see https://github.com/astral-sh/setup-uv?tab=readme-ov-file#enable-caching

.github/workflows/main.yml

@@ -40,6 +40,8 @@ jobs:
         python-version: ${{ matrix.python-version }}
 
     - uses: astral-sh/setup-uv@v5
+      with:
+        enable-cache: false  # we don't have lock files, so can't use them as cache key
 
     - uses: actions/checkout@v4
       with:
@@ -75,6 +77,8 @@ jobs:
         python-version: '3.10'
 
     - uses: astral-sh/setup-uv@v5
+      with:
+        enable-cache: false  # we don't have lock files, so can't use them as cache key
 
     - uses: actions/checkout@v4
       with: