Minor spelling fixes

Reviewing my recent update in gedit showed a few spelling typos
in code-update.md.  I also noticed the possible auto-correct
that put a backquote before an e in rest-api.md.  After that I
ran the remaining files through gedit looking for mis-spelled
words and found a few with missing letters.

Signed-off-by: Milton Miller <miltonm@us.ibm.com>
diff --git a/code-update.md b/code-update.md
index 28f351f..b599474 100644
--- a/code-update.md
+++ b/code-update.md
@@ -50,7 +50,7 @@
 RAM so the images can be applied while the rest of the application stack
 is running and progress can be monitored over the network.  The
 `update` script can then be called to write the images while the
-system is operational and its progress ouput monitored.
+system is operational and its progress output monitored.
 
 Update from the OpenBMC shell
 -----------------------------
@@ -112,7 +112,7 @@
  * `preserve_network_settings`: Preserve network settings, only needed if updating the whole flash
  * `restore_application_defaults`: update (clear) the read-write file system
  * `update_kernel_and_apps_only`: update kernel and initramfs
- * `clear_persistent_files`: ignore the persistent file list when reseting applications defaults
+ * `clear_persistent_files`: ignore the persistent file list when resetting applications defaults
  * `auto_apply`: Attempt to write the images by invoking the `Apply` method after the images are unpacked.
 
 To configure the update settings, perform a REST PUT to
diff --git a/contributing.md b/contributing.md
index 195bde6..f2e2c83 100644
--- a/contributing.md
+++ b/contributing.md
@@ -88,7 +88,7 @@
 Submitting changes via Gerrit server
 ------------------------------------
 
-The openbmc gerrit server supports Gihub credentials, its link is:
+The openbmc gerrit server supports Github credentials, its link is:
 
   https://gerrit.openbmc-project.xyz/#/q/status:open
 
@@ -156,7 +156,7 @@
 Best practices for C
 --------------------
 
-There are numerous resources avaialble elsewhere, but a few items that are
+There are numerous resources available elsewhere, but a few items that are
 relevant to OpenBMC work:
 
  * You almost never need to use `system(<some shell pipeline>)`. Reading and
@@ -174,7 +174,7 @@
    C types
 
  * Declare internal-only functions as `static`, declare read-only data
-   as `const` where possble.
+   as `const` where possible.
 
  * Ensure that your code compiles without warnings, especially for changes
    to the kernel.
diff --git a/rest-api.md b/rest-api.md
index 10b01e9..4fe2e02 100644
--- a/rest-api.md
+++ b/rest-api.md
@@ -178,7 +178,7 @@
 DELETE operations are for removing instances. Only DBUS objects (instances) can
 be removed. If the underlying DBUS object implements the
 `org.openbmc.Object.Delete` interface the REST server will call it. If
-`org.openbmc.Object.Delet`e is not implemented, the REST server will return a
+`org.openbmc.Object.Delete` is not implemented, the REST server will return a
 HTTP 403 (Forbidden) error.
 
 For example, to delete the event record with ID 0: