Fix configgen.sh to handle all example repository names

Updated sed pattern from 's/.*examples[^/]*\///g' to 's/.*example[^/]*\///g'
to match both:
- envoy_examples (plural)
- envoy_example_wasm_cc (singular)

This fixes the docs build genrule failure in envoy_examples where files from
envoy_example_wasm_cc repository weren't being processed correctly.

The pattern now matches "example" (with or without 's') followed by any
non-slash characters and a slash, working in both WORKSPACE and bzlmod modes.

Co-authored-by: phlax <454682+phlax@users.noreply.github.com>

Author: Copilot

configs/configgen.sh

@@ -30,7 +30,7 @@ for FILE in "$@"; do
     ;;
   *)
 
-    FILENAME="$(echo "$FILE" | sed -e 's/.*examples[^/]*\///g')"
+    FILENAME="$(echo "$FILE" | sed -e 's/.*example[^/]*\///g')"
     # Configuration filenames may conflict. To avoid this we use the full path.
     cp "$FILE" "$OUT_DIR/${FILENAME//\//_}"
     ;;