revert pyth anchor ver, dependency issues

oracles/pyth/anchor/programs/pythexample/Cargo.toml

@@ -14,9 +14,8 @@ cpi = ["no-entrypoint"]
 no-entrypoint = []
 no-idl = []
 no-log-ix-name = []
-idl-build = ["anchor-lang/idl-build", "anchor-spl/idl-build"]
 
 [dependencies]
-anchor-lang = "0.30.0"
+anchor-lang = "0.28.0"
 pyth-sdk-solana = "0.8.0"
 pyth-sdk = "0.8.0"