Fix the name of a variable in 'basics.adoc'

Author: asensi

doc/modules/ROOT/pages/basics.adoc

@@ -39,7 +39,7 @@ Overflow and underflow are handled the same way that they are with binary floati
 
 [source, c++]
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-boost::decimal::decimal64_t oveflow_value {100, 10000}; // Constructs +infinity
+boost::decimal::decimal64_t overflow_value {100, 10000}; // Constructs +infinity
 boost::decimal::decimal64_t underflow_value {100, -10000}; // Constructs 0
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