Improve wording and spelling consistency in UPGRADING

[ci skip]

Author: theodorejb

UPGRADING

@@ -217,26 +217,24 @@ PHP 8.0 UPGRADE NOTES
  . debug_backtrace() and Exception::getTrace() will no longer provide
  references to arguments. It will not be possible to change function
  arguments through the backtrace.
- . The concept of numeric-string has been altered to be less error prone.
- Trailing whitespaces are now allowed in numeric strings making it symmetric
- with how leading whitespaces were treated.
- This mostly affects:
+ . Numeric string handling has been altered to be more intuitive and less
+ error-prone. Trailing whitespace is now allowed in numeric strings for
+ consistency with how leading whitespace is treated. This mostly affects:
  - The is_numeric() function
  - String-to-string comparisons
  - Type declarations
- - Increment and Decrement operations
- The concept of "leading-numeric string" has been mostly dropped, the cases
- where this concept remains is in order to ease migration.
- String which emitted an E_NOTICE "A non well formed numeric value encountered"
- will now emit an E_WARNING "A non-numeric value encountered"
- and all strings which emitted an E_WARNING "A non-numeric value encountered"
- will now throw a TypeError.
- This mostly affects:
+ - Increment and decrement operations
+ The concept of a "leading-numeric string" has been mostly dropped; the
+ cases where this remains exist in order to ease migration. Strings which
+ emitted an E_NOTICE "A non well formed numeric value encountered" will now
+ emit an E_WARNING "A non-numeric value encountered" and all strings which
+ emitted an E_WARNING "A non-numeric value encountered" will now throw a
+ TypeError. This mostly affects:
  - Arithmetic operations
  - Bitwise operations
  This E_WARNING to TypeError change also affects the E_WARNING
- "Illegal string offset 'string'" for illegal string offsets.
- This does not change the behaviour of explicit casts to int/float from strings.
+ "Illegal string offset 'string'" for illegal string offsets. The behavior
+ of explicit casts to int/float from strings has not been changed.
  RFC: https://wiki.php.net/rfc/saner-numeric-strings
 
 - COM:
@@ -356,7 +354,7 @@ PHP 8.0 UPGRADE NOTES
  now be empty.
  . The $is_hex parameter, which was not used internally, has been removed from
  mb_decode_numericentity().
- . The legacy behaviour of passing the encoding as the third argument instead
+ . The legacy behavior of passing the encoding as the third argument instead
  of an offset for the mb_strrpos() function has been removed, provide an
  explicit 0 offset with the encoding as the fourth argument instead.
  . The ISO_8859-* character encoding aliases have been replaced by ISO8859-*
@@ -370,7 +368,7 @@ PHP 8.0 UPGRADE NOTES
 
 - PCRE:
  . When passing invalid escape sequences they are no longer interpreted as
- literals. This behaviour previously required the X modifier - which is
+ literals. This behavior previously required the X modifier - which is
  now ignored.
 
 - PDO: