Fix code-block:: c with lowercase c for sphinx (Qiskit#14593)

Author: Cryoris

docs/cdoc/qk-target-entry.rst

@@ -3,7 +3,7 @@
 QkTargetEntry
 =============
 
-.. code-block:: C
+.. code-block:: c
 
     typedef struct QkTargetEntry QkTargetEntry
 
@@ -13,7 +13,7 @@ from C.
 
 Here's an example of how this structure works:
 
-.. code-block:: C
+.. code-block:: c
 
     #include <qiskit.h>
     #include <math.h>
@@ -34,4 +34,4 @@ Functions
 
 .. doxygengroup:: QkTargetEntry
     :members:
-    :content-only:
+    :content-only:

docs/cdoc/qk-target.rst

@@ -2,7 +2,7 @@
 QkTarget
 ========
 
-.. code-block:: C
+.. code-block:: c
 
     typedef struct QkTarget QkTarget
 
@@ -15,7 +15,7 @@ counterpart, :class:`.Target`.
 
 Here's an example of how this structure works:
 
-.. code-block:: C
+.. code-block:: c
 
     #include <qiskit.h>
     #include <math.h>