git: ignore all `target/` directories (#34705)

git: ignore all target directories

.gitignore

@@ -1,9 +1,9 @@
 farf/
+target/
 /solana-release/
 /solana-release.tar.bz2
 /solana-metrics/
 /solana-metrics.tar.bz2
-/target/
 /test-ledger/
 
 **/*.rs.bk