Correct the count of operations gRPC cannot serve, and the punctuation around them

[tonytonycoder11]

Two passes over the prose. No behaviour change, one KDoc touched.

The count was wrong

GrpcQdrantTransport's KDoc said eleven operations have no gRPC equivalent. There are fourteen. The
number was written from memory and never checked, and from that KDoc it reached the README,
STABILITY.md, the migration guide and the changelog.

grep -o 'restOnly("[a-zA-Z]*")' GrpcQdrantTransport.kt | sort -u | wc -l
14

Two things made it wrong. The enumeration said "the five shard-scope snapshot operations" and there are
six, because recoverShardSnapshot was missing. And downloadStorageSnapshot was left out of the list
altogether.

The enumeration now follows how the code groups them, so the next reader can arrive at fourteen without
reconstructing the list: the two issues calls, the snapshot and storage-snapshot transfers, and the six
shard-scope operations.

Punctuation and emphasis

Twenty-two em dashes across the same files, several of them standing in for two different marks inside
one sentence. Each is replaced by what the sentence wanted: a colon where a list follows, a full stop
between two independent clauses, commas around a genuine aside.

File	em dashes	boldface
README.md	8 → 1	8 → 7
STABILITY.md	8 → 0	19 → 9
docs/migrating-from-qdrant-client.md	5 → 0	0
CONTRIBUTING.md	1 → 0	0
CHANGELOG.md, [2.0.0] only	4 → 0	8 → 7

The one left in the README is the status blockquote, whose shape STANDARD.md prescribes and
audit-library.sh greps for.

STABILITY.md had nine paragraphs opening with a bolded sentence doing the work of a heading. When
every paragraph carries an emphasised line, none of them is emphasised. What survives marks MAJOR,
MINOR and PATCH, where the bold separates a defined term from its definition.

Changelog sections before 2.0.0 are left alone: their text generated the GitHub Release bodies at the
time, and rewriting them would leave the two disagreeing about a release nobody can cut again.

./gradlew build green, audit At standard. The v2.0.0 Release body needs regenerating from the
corrected changelog after merge.