qapi/block: Tidy up block-latency-histogram-set documentation

Examples come out like

    Example

       set new histograms for all io types with intervals [0, 10), [10,
       50), [50, 100), [100, +inf):

The sentence "set new histograms ..." starts with a lower case letter.
Capitalize it.  Same for the other examples.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-ID: <20230720071610.1096458-3-armbru@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>

qapi/block.json

@@ -547,7 +547,7 @@
 #
 # Example:
 #
-# set new histograms for all io types with intervals [0, 10), [10,
+# Set new histograms for all io types with intervals [0, 10), [10,
 # 50), [50, 100), [100, +inf):
 #
 # -> { "execute": "block-latency-histogram-set",
@@ -557,7 +557,7 @@
 #
 # Example:
 #
-# set new histogram only for write, other histograms will remain not
+# Set new histogram only for write, other histograms will remain not
 # changed (or not created):
 #
 # -> { "execute": "block-latency-histogram-set",
@@ -567,7 +567,7 @@
 #
 # Example:
 #
-# set new histograms with the following intervals:   read, flush: [0,
+# Set new histograms with the following intervals:   read, flush: [0,
 # 10), [10, 50), [50, 100), [100, +inf)   write: [0, 1000), [1000,
 # 5000), [5000, +inf)
 #
@@ -579,7 +579,7 @@
 #
 # Example:
 #
-# remove all latency histograms:
+# Remove all latency histograms:
 #
 # -> { "execute": "block-latency-histogram-set",
 #      "arguments": { "id": "drive0" } }