Manual: Shorten Introduction

* doc/org.texi: Remove one useless piece from the introduction.  Modify
a paragraph about key bidings.

doc/org.texi

@@ -826,11 +826,6 @@ makes it uniquely suited for authoring technical documents with code
 examples.  It facilitates code evaluation, capturing code output into the
 document, documentation, and literate programming techniques.
 
-Org has its roots in the practical desire of a scientist to organize his life
-and work.  Over the past ten years it has been shaped by a community of
-truely excellent people who have expanded and deepened its applications and
-clarified its implementation.
-
 Org keeps simple things simple.  When first fired up, it should feel like a
 straightforward, easy to use outliner.  Complexity is not imposed, but a
 large amount of functionality is available when you need it.  Org is a
@@ -1127,9 +1122,10 @@ templates insert lowercase keywords and Babel dynamically inserts
 @kindex C-c c
 @findex org-capture
 
-The manual suggests two global keybindings: @kbd{C-c a} for @code{org-agenda}
-and @kbd{C-c c} for @code{org-capture}.  These are only suggestions, but the
-rest of the manual assumes that you are using these keybindings.
+The manual suggests a few global keybindings, in particular @kbd{C-c a} for
+@code{org-agenda} and @kbd{C-c c} for @code{org-capture}.  These are only
+suggestions, but the rest of the manual assumes that these keybindings are in
+place.
 
 Also, the manual lists both the keys and the corresponding commands for
 accessing a functionality.  Org mode often uses the same key for different