set heading sizes

ui/home/LatestBlocks.tsx

@@ -101,7 +101,7 @@ const LatestBlocks = () => {
 
   return (
     <>
-      <Heading as="h4" fontSize="18px" mb={{ base: 3, lg: 8 }}>Latest Blocks</Heading>
+      <Heading as="h4" size="sm" mb={{ base: 4, lg: 7 }}>Latest Blocks</Heading>
       { content }
     </>
   );

ui/home/LatestTxs.tsx

@@ -54,7 +54,7 @@ const LatestTransactions = () => {
 
   return (
     <>
-      <Heading as="h4" fontSize="18px" mb={{ base: 3, lg: 8 }}>Latest transactions</Heading>
+      <Heading as="h4" size="sm" mb={ 4 }>Latest transactions</Heading>
       { content }
     </>
   );

ui/txs/TxAdditionalInfo.tsx

@@ -28,7 +28,7 @@ const TxAdditionalInfo = ({ tx }: { tx: Transaction }) => {
 
   return (
     <>
-      <Heading as="h4" fontSize="18px" mb={ 6 }>Additional info </Heading>
+      <Heading as="h4" size="sm" mb={ 6 }>Additional info </Heading>
       <Box { ...sectionProps } mb={ 4 }>
         <Text { ...sectionTitleProps }>Transaction fee</Text>
         <Flex>