fix a couple feature gates

New versions of rustc detect invalid feature gates. We had two, which
resulted in tests that were never run.

Author: apoelstra

src/blech32/decode.rs

@@ -889,13 +889,12 @@ mod tests {
     }
 
     #[test]
-    #[cfg(feature = "alloc")]
     fn check_hrp_max_length() {
         let hrps =
             "an83characterlonghumanreadablepartthatcontainsthenumber1andtheexcludedcharactersbio";
 
         let hrp = Hrp::parse_unchecked(hrps);
-        let s = crate::encode::<Blech32>(hrp, &[]).expect("failed to encode empty buffer");
+        let s = crate::bech32::encode::<Blech32>(hrp, &[]).expect("failed to encode empty buffer");
 
         let unchecked = UncheckedHrpstring::new(&s).expect("failed to parse address");
         assert_eq!(unchecked.hrp(), hrp);

src/block.rs

@@ -434,15 +434,15 @@ mod tests {
             000000000000000000000000000000000000\
             ";
 
-    #[cfg(feature = "serde-feature")]
+    #[cfg(feature = "serde")]
     #[test]
     fn blockheader_serde() {
         let block: Block = hex_deserialize!(&SIMPLE_BLOCK);
         roundtrip_header(&block.header);
         let block: Block = hex_deserialize!(&DYNAFED_BLOCK);
         roundtrip_header(&block.header);
     }
-    #[cfg(feature = "serde-feature")]
+    #[cfg(feature = "serde")]
     fn roundtrip_header(header: &BlockHeader) {
         let header_ser = serde_json::to_string(header).unwrap();
         let header_deser: BlockHeader = serde_json::from_str(&header_ser).unwrap();