Clean up for BigInteger (#8215)

- Remove "subtraction", which is duplicated
- Remove "negation", which is equivalent to "unary negation"

Author: GitHubPang

xml/System.Numerics/BigInteger.xml

@@ -263,7 +263,7 @@
  The uninitialized value of a <xref:System.Numerics.BigInteger> is <xref:System.Numerics.BigInteger.Zero%2A>.  
 
 ## Performing Operations on BigInteger Values  
- You can use a <xref:System.Numerics.BigInteger> instance as you would use any other integral type. <xref:System.Numerics.BigInteger> overloads the standard numeric operators to enable you to perform basic mathematical operations such as addition, subtraction, division, multiplication, subtraction, negation, and unary negation. You can also use the standard numeric operators to compare two <xref:System.Numerics.BigInteger> values with each other. Like the other integral types, <xref:System.Numerics.BigInteger> also supports the bitwise `And`, `Or`, `XOr`, left shift, and right shift operators. For languages that do not support custom operators, the <xref:System.Numerics.BigInteger> structure also provides equivalent methods for performing mathematical operations. These include <xref:System.Numerics.BigInteger.Add%2A>, <xref:System.Numerics.BigInteger.Divide%2A>, <xref:System.Numerics.BigInteger.Multiply%2A>, <xref:System.Numerics.BigInteger.Negate%2A>, <xref:System.Numerics.BigInteger.Subtract%2A>, and several others.  
+ You can use a <xref:System.Numerics.BigInteger> instance as you would use any other integral type. <xref:System.Numerics.BigInteger> overloads the standard numeric operators to enable you to perform basic mathematical operations such as addition, subtraction, division, multiplication, and unary negation. You can also use the standard numeric operators to compare two <xref:System.Numerics.BigInteger> values with each other. Like the other integral types, <xref:System.Numerics.BigInteger> also supports the bitwise `And`, `Or`, `XOr`, left shift, and right shift operators. For languages that do not support custom operators, the <xref:System.Numerics.BigInteger> structure also provides equivalent methods for performing mathematical operations. These include <xref:System.Numerics.BigInteger.Add%2A>, <xref:System.Numerics.BigInteger.Divide%2A>, <xref:System.Numerics.BigInteger.Multiply%2A>, <xref:System.Numerics.BigInteger.Negate%2A>, <xref:System.Numerics.BigInteger.Subtract%2A>, and several others.  
 
  Many members of the <xref:System.Numerics.BigInteger> structure correspond directly to members of the other integral types. In addition, <xref:System.Numerics.BigInteger> adds members such as the following: