Remove extraneous quotation marks

These appear in --help and in
https://gn.googlesource.com/gn/+/master/docs/reference.md#var_output_conversion.

TESTED=built, then `out/gn help output_conversion`

Change-Id: I82aba71a7e9725f3e3228e679eb81a23c2fbffe1
Reviewed-on: https://gn-review.googlesource.com/c/gn/+/7200
Reviewed-by: Brett Wilson <brettw@chromium.org>
Commit-Queue: Brett Wilson <brettw@chromium.org>

docs/reference.md

diff --git a/docs/reference.md b/docs/reference.md
index 7abdd20..5c2223a 100644
--- a/docs/reference.md
+++ b/docs/reference.md
@@ -5639,7 +5639,7 @@
     }
   }
 ```
-### <a name="var_output_conversion"></a>**"output_conversion**: Data format for generated_file targets.
+### <a name="var_output_conversion"></a>**output_conversion**: Data format for generated_file targets.
 
 ```
   Controls how the "contents" of a generated_file target is formatted.

src/gn/variables.cc

diff --git a/src/gn/variables.cc b/src/gn/variables.cc
index 08509ea..b6293b4 100644
--- a/src/gn/variables.cc
+++ b/src/gn/variables.cc
@@ -2128,7 +2128,7 @@
 const char kWriteOutputConversion_HelpShort[] =
     "output_conversion: Data format for generated_file targets.";
 const char kWriteOutputConversion_Help[] =
-    R"("output_conversion: Data format for generated_file targets.
+    R"(output_conversion: Data format for generated_file targets.
 
   Controls how the "contents" of a generated_file target is formatted.
   See "gn help io_conversion".