Renamed "usee" to "uee".

The naturalize tool detected that using "uee" is more consistent with
the current codebase state:
* "uee" in LocalStore is 28.47% probable ("usee" 5.01%)
* "uee" in TextBody is 45.02% probable ("usee" 9.10%)

src/com/fsck/k9/mail/internet/TextBody.java

@@ -63,7 +63,7 @@ public class TextBody implements Body {
                 b = EMPTY_BYTE_ARRAY;
             }
             return new ByteArrayInputStream(b);
-        } catch (UnsupportedEncodingException usee) {
+        } catch (UnsupportedEncodingException uee) {
             return null;
         }
     }

src/com/fsck/k9/mail/store/LocalStore.java

@@ -1068,7 +1068,7 @@ public class LocalStore extends Store implements Serializable {
                     return null;
                 }
             });
-        } catch (UnsupportedEncodingException usee) {
+        } catch (UnsupportedEncodingException uee) {
             throw new Error("Aparently UTF-8 has been lost to the annals of history.");
         }
     }