minor #7788 Update performance.rst (eugestarr)

This PR was submitted for the 2.8 branch but it was merged into the 2.7 branch instead (closes #7788).

Discussion
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Update performance.rst

Minor grammar updates

Commits
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f2fc3d0 Update performance.rst

Author: xabbuh

performance.rst

@@ -79,7 +79,7 @@ real and absolute file system paths. This increases the performance for
 applications like Symfony that open many PHP files, especially on Windows
 systems.
 
-By default PHP sets a ``realpath_cache_size`` of ``16K`` which is too low for
+By default, PHP sets a ``realpath_cache_size`` of ``16K`` which is too low for
 Symfony. Consider updating this value at least to ``4096K``. In addition, cached
 paths are only stored for ``120`` seconds by default. Consider updating this
 value too using the ``realpath_cache_ttl`` option:
@@ -195,7 +195,7 @@ Bootstrap Files and Byte Code Caches
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 Even when using a byte code cache, performance will improve when using a bootstrap
-file since there will be fewer files to monitor for changes. Of course if this
+file since there will be fewer files to monitor for changes. Of course, if this
 feature is disabled in the byte code cache (e.g. ``apc.stat=0`` in APC), there
 is no longer a reason to use a bootstrap file.