Pin numpy in setup.py to pre 2.0 (#5579)

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**Context:** With the numpy 2.0 release coming soon, we will aim to pin
PennyLane until post-release validation can be performed.

**Description of the Change:** As above.

**Benefits:**

**Possible Drawbacks:**

**Related GitHub Issues:**

Co-authored-by: Astral Cai <[email protected]>

setup.py

@@ -21,7 +21,7 @@
     version = f.readlines()[-1].split()[-1].strip("\"'")
 
 requirements = [
-    "numpy",
+    "numpy<2.0",
     "scipy",
     "networkx",
     "rustworkx",