Fix highlighting

Author: mborland

doc/modules/ROOT/pages/decimal128_t.adoc

@@ -10,7 +10,7 @@ https://www.boost.org/LICENSE_1_0.txt
 
 == Description
 
-decimal128_t is the 128-bit version of the decimal interchange format, and has the following properties as defined in IEEE 754-2019 table 3.6
+`decimal128_t` is the 128-bit version of the decimal interchange format, and has the following properties as defined in IEEE 754-2019 table 3.6
 
 |===
 | Attribute | values

doc/modules/ROOT/pages/decimal32_t.adoc

@@ -10,7 +10,7 @@ https://www.boost.org/LICENSE_1_0.txt
 
 == Description
 
-decimal32_t is the 32-bit version of the decimal interchange format, and has the following properties as defined in IEEE 754-2019 table 3.6
+`decimal32_t` is the 32-bit version of the decimal interchange format, and has the following properties as defined in IEEE 754-2019 table 3.6
 
 |===
 | Attribute | values

doc/modules/ROOT/pages/decimal64_t.adoc

@@ -10,7 +10,7 @@ https://www.boost.org/LICENSE_1_0.txt
 
 == Description
 
-decimal64_t is the 64-bit version of the decimal interchange format, and has the following properties as defined in IEEE 754-2019 table 3.6
+`decimal64_t` is the 64-bit version of the decimal interchange format, and has the following properties as defined in IEEE 754-2019 table 3.6
 
 |===
 | Attribute | values