change file location for showcase patch for light (#12456)

# Objective

- in https://github.com/bevyengine/bevy/pull/12369, patched file changed
location, so patch is failing

## Solution

- fix patch

tools/example-showcase/reduce-light-cluster-config.patch

@@ -1,8 +1,8 @@
-diff --git a/crates/bevy_pbr/src/light.rs b/crates/bevy_pbr/src/light.rs
-index 3e8c0d451..07aa7d586 100644
---- a/crates/bevy_pbr/src/light.rs
-+++ b/crates/bevy_pbr/src/light.rs
-@@ -694,8 +694,8 @@ impl Default for ClusterConfig {
+diff --git a/crates/bevy_pbr/src/light/mod.rs b/crates/bevy_pbr/src/light/mod.rs
+index 5d6be4fcf..fe20a5dc5 100644
+--- a/crates/bevy_pbr/src/light/mod.rs
++++ b/crates/bevy_pbr/src/light/mod.rs
+@@ -759,8 +759,8 @@ impl Default for ClusterConfig {
          // 24 depth slices, square clusters with at most 4096 total clusters
          // use max light distance as clusters max `Z`-depth, first slice extends to 5.0
          Self::FixedZ {