[clang-format] [NFC] Fix spelling and grammatical errors in IncludeBlocks text

[MyDeveloperDay]

Summary

Fix spelling mistake
Leave space after . and before beginning of next sentence
Reword it slightly to try and make it more readable.
Ensure RST is updated correctly (it generated a change)

[HazardyKnusperkeks]

I have only one question, what stands NFC for? I figured something like "no functional change"? But I can't find a definition anywhere.

[curdeius]

In D92822#2439069, @HazardyKnusperkeks wrote:

I have only one question, what stands NFC for? I figured something like "no functional change"? But I can't find a definition anywhere.

https://www.llvm.org/docs/Lexicon.html#nfc

clang/docs/ClangFormatStyleOptions.rst

**IncludeCategories** (``std::vector<IncludeCategory>``)
   If none of the regular expressions match, INT_MAX is assigned as
   category. The main header for a source file automatically gets category 0.
   so that it is generally kept at the beginning of the ``#includes``
   (https://llvm.org/docs/CodingStandards.html#include-style). However, you
   can also assign negative priorities if you have certain headers that
   always need to be first.
 
   There is a third and optional field ``SortPriority`` which can used while
-  ``IncludeBloks = IBS_Regroup`` to define the priority in which ``#includes``
-  should be ordered, and value of ``Priority`` defines the order of
-  ``#include blocks`` and also enables to group ``#includes`` of different
-  priority for order.``SortPriority`` is set to the value of ``Priority``
-  as default if it is not assigned.
+  ``IncludeBlocks = IBS_Regroup`` to define the priority in which
+  ``#includes`` should be ordered. The value of ``Priority`` defines the
+  order of ``#include blocks`` and also allows the grouping of ``#includes``
+  of different priority. ``SortPriority`` is set to the value of
+  ``Priority`` as default if it is not assigned.
 
   Each regular expression can be marked as case sensitive with the field
   ``CaseSensitive``, per default it is not.
 
   To configure this in the .clang-format file, use:
 
   .. code-block:: yaml
 

clang/include/clang/Tooling/Inclusions/IncludeStyle.h

struct IncludeStyle {
   /// If none of the regular expressions match, INT_MAX is assigned as
   /// category. The main header for a source file automatically gets category 0.
   /// so that it is generally kept at the beginning of the ``#includes``
   /// (https://llvm.org/docs/CodingStandards.html#include-style). However, you
   /// can also assign negative priorities if you have certain headers that
   /// always need to be first.
   ///
   /// There is a third and optional field ``SortPriority`` which can used while
-  /// ``IncludeBloks = IBS_Regroup`` to define the priority in which
-  /// ``#includes`` should be ordered, and value of ``Priority`` defines the
-  /// order of
-  /// ``#include blocks`` and also enables to group ``#includes`` of different
-  /// priority for order.``SortPriority`` is set to the value of ``Priority``
-  /// as default if it is not assigned.
+  /// ``IncludeBlocks = IBS_Regroup`` to define the priority in which
+  /// ``#includes`` should be ordered. The value of ``Priority`` defines the
+  /// order of ``#include blocks`` and also allows the grouping of ``#includes``
+  /// of different priority. ``SortPriority`` is set to the value of
+  /// ``Priority`` as default if it is not assigned.
   ///
   /// Each regular expression can be marked as case sensitive with the field
   /// ``CaseSensitive``, per default it is not.
   ///
   /// To configure this in the .clang-format file, use:
   /// \code{.yaml}
   ///   IncludeCategories:
   ///     - Regex:           '^"(llvm|llvm-c|clang|clang-c)/'