Remove superfluous quote from ECHO in bootstrap.bat

Fixes accidental left over in PR #182

Cherry-pick PR #227 to master

bootstrap.bat

@@ -52,7 +52,7 @@ IF "%1"=="vc14" SET TOOLSET=msvc : 14.0
 IF "%1"=="vc141" SET TOOLSET=msvc : 14.1
 
 ECHO.
-ECHO Generating Boost.Build configuration in project-config.jam for %TOOLSET%..."
+ECHO Generating Boost.Build configuration in project-config.jam for %TOOLSET%...
 ECHO # Boost.Build Configuration > project-config.jam
 ECHO # Automatically generated by bootstrap.bat >> project-config.jam
 ECHO. >> project-config.jam